If you set up a field attribute set and associate that set with a field in your table that will work. If you set the value in the object inspector it will let you enter in a string but it will not reflect the value at runtime. If you try to set the TField.DefaultExpression property at runtime like this: MyField.DefaultExpression := 'MyValue'; It will compile but you will not get a default value at runtime when you create a new record in the table by, say, clicking on the + on the DBNavigator. To get the default value to take at runtime the code assignment needs to be: MyField.DefaultExpression := '''MyValue'''; In the Object Inspector. You just need to put 'MyValue'. Use single quotes in the Object Inspector.