diff --git a/Sources/DataAccess/DataTableBuilder.cs b/Sources/DataAccess/DataTableBuilder.cs
index 0601d80..1cf4aed 100644
--- a/Sources/DataAccess/DataTableBuilder.cs
+++ b/Sources/DataAccess/DataTableBuilder.cs
@@ -115,11 +115,11 @@ public static MutableDataTable GetMutableCopy(this DataTableBuilder builder, Dat
         /// <param name="builder">ignored</param>
         /// <param name="filename">filename of table to load. Schema is inferred from header row.</param>
         /// <returns>a in-memory table containing the topN rows from the supplied file.</returns>
-        public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, string filename)
+        public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, string filename, char columnSeparator = default (char))
         {
-            return ReadSampleTopN(builder, filename, 100);
+            return ReadSampleTopN(builder, filename, columnSeparator, 100);
         }
-        
+
         /// <summary>
         /// Return an in-memory table that contains the topN rows from the table in the filename.
         /// </summary>
@@ -127,7 +127,7 @@ public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, str
         /// <param name="filename">filename of table to load. Schema is inferred from header row.</param>
         /// <param name="topN">reads the topN rows from the table.</param>
         /// <returns>a in-memory table containing the topN rows from the supplied file.</returns>
-        public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, string filename, int topN = 100)
+        public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, string filename, char columnSeparator = default(char), int topN = 100)
         {
             Debug.Assert(builder != null);
             if (filename == null)
@@ -135,7 +135,7 @@ public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, str
                 throw new ArgumentNullException("filename");
             }
 
-            DataTable source = new FileStreamingDataTable(filename);
+            DataTable source = new FileStreamingDataTable(filename, columnSeparator);
             MutableDataTable dt = Analyze.SampleTopN(source, topN);
             return dt;
         }
@@ -147,11 +147,11 @@ public static MutableDataTable ReadSampleTopN(this DataTableBuilder builder, str
         /// <param name="builder"></param>
         /// <param name="filename">filename of CSV to read</param>
         /// <returns>a streaming data table for the given filename</returns>
-        public static DataTable ReadLazy(this DataTableBuilder builder, string filename)
+        public static DataTable ReadLazy(this DataTableBuilder builder, string filename, char columnSeparator = default(char))
         {
             Debug.Assert(builder != null);
 
-            return new FileStreamingDataTable(filename) { Name = filename };
+            return new FileStreamingDataTable(filename, columnSeparator) { Name = filename };
         }
 
         /// <summary>
@@ -161,14 +161,13 @@ public static DataTable ReadLazy(this DataTableBuilder builder, string filename)
         /// <param name="builder"></param>
         /// <param name="inputStream">input stream. Must be seekable and readable</param>
         /// <returns>a streaming data table for the given filename</returns>
-        public static DataTable ReadLazy(this DataTableBuilder builder, Stream inputStream)
+        public static DataTable ReadLazy(this DataTableBuilder builder, Stream inputStream, char columnSeparator = default(char))
         {
             Debug.Assert(builder != null);
 
-            return new StreamingDataTable(inputStream);
+            return new StreamingDataTable(inputStream, columnSeparator);
         }
 
-        
         /// <summary>        
         /// Create an in-memory table with 2 columns (key and value), where each row is a KeyValuePair from the dictionary.         
         /// </summary>
diff --git a/Sources/DataAccess/Readers.cs b/Sources/DataAccess/Readers.cs
index dd3879e..dc396ef 100644
--- a/Sources/DataAccess/Readers.cs
+++ b/Sources/DataAccess/Readers.cs
@@ -1,8 +1,10 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Text;
 
+
 namespace DataAccess
 {
 
@@ -225,24 +227,15 @@ public static MutableDataTable Read(TextReader stream, char delimiter = '\0')
 
         public static char GuessSeparateFromHeaderRow(string header)
         {
-            if (header.Contains("\t"))
-            {
-                return '\t';
-            }
-
-            if (header.Contains(","))
-            {
-                return ',';
-            }
-
-            if (header.Contains(";"))
-            {
-                return ';';
-            }
-            
-            // Fallback is always comma. This implies a single column. 
-            return ',';
-            
+            var validSeparators = new[] { '\t', ',', ';' };
+                    
+            var firstSeparator =
+            (from x in validSeparators.Select(c => new { separator = c, index = header.IndexOf(c) })
+            where x.index >= 0
+            orderby x.index
+            select x.separator).ToList();
+
+            return firstSeparator.Any() ? firstSeparator.FirstOrDefault() : ',';
         }
 
         // Read in a Ascii file that uses the given separate characters.
diff --git a/Sources/DataAccess/StreamingDataTable.cs b/Sources/DataAccess/StreamingDataTable.cs
index 875c579..fcfb13a 100644
--- a/Sources/DataAccess/StreamingDataTable.cs
+++ b/Sources/DataAccess/StreamingDataTable.cs
@@ -15,7 +15,8 @@ internal class StreamingDataTable : TextReaderDataTable
     {
         readonly Stream _input;
 
-        public StreamingDataTable(Stream input)
+        public StreamingDataTable(Stream input, char columnSeparator)
+            : base(columnSeparator)
         {
             // We could optimize to avoid requiring CanSeek if we failed on attemps
             // to read the the rows multiple times. 
@@ -30,7 +31,7 @@ protected override TextReader OpenText()
         {
             _input.Position = 0;
 
-            
+
             return new StreamReader(_input);
         }
         protected override void CloseText(TextReader reader)
@@ -43,8 +44,9 @@ protected override void CloseText(TextReader reader)
     internal class FileStreamingDataTable : TextReaderDataTable
     {
         private readonly string _filename;
-        
-        public FileStreamingDataTable(string filename)
+
+        public FileStreamingDataTable(string filename, char columnSeparator)
+            : base(columnSeparator)
         {
             _filename = filename;
         }
@@ -65,9 +67,15 @@ protected override void CloseText(TextReader reader)
     /// </summary>
     internal abstract class TextReaderDataTable : DataTable
     {
+        private readonly char columnSeparator;
+
         private string[] _names;
 
-        
+        protected TextReaderDataTable(char columnSeparator)
+        {
+            this.columnSeparator = columnSeparator;
+        }
+
         public override IEnumerable<string> ColumnNames
         {
             get
@@ -77,10 +85,10 @@ public override IEnumerable<string> ColumnNames
                     TextReader sr = null;
                     try
                     {
-                        sr = this.OpenText();                    
+                        sr = this.OpenText();
                         // First get columns.
                         string header = sr.ReadLine();
-                        char ch = Reader.GuessSeparateFromHeaderRow(header);
+                        char ch = this.columnSeparator == default(char) ? Reader.GuessSeparateFromHeaderRow(header) : this.columnSeparator;
                         _names = Reader.split(header, ch);
                     }
                     finally
@@ -100,7 +108,7 @@ public override IEnumerable<string> ColumnNames
         // called on reader from OpenText
         // Don't call dipose because that can close streams. 
         protected abstract void CloseText(TextReader reader);
-        
+
         public override IEnumerable<Row> Rows
         {
             get
@@ -113,7 +121,7 @@ public override IEnumerable<Row> Rows
                     sr = this.OpenText();
 
                     string header = sr.ReadLine(); // skip past header
-                    char chSeparator = Reader.GuessSeparateFromHeaderRow(header);
+                    char chSeparator = this.columnSeparator == default(char) ? Reader.GuessSeparateFromHeaderRow(header) : this.columnSeparator;
 
                     int illegal = 0;
                     string line;
@@ -124,7 +132,7 @@ public override IEnumerable<Row> Rows
                         {
 
                             string[] parts = Reader.split(line, chSeparator);
-                            
+
                             // $$$ Major hack for dealing with newlines in quotes strings.
                             // The better fix here would be to switch to a streaming interface.
                             if (parts.Length != columnCount)