>Oh gosh, it couldn't be that simple could it? I'll test it - thanks Stefan!

Actually I was not sure when I read your description, so I'm happy you did not laugh at me :-)
FWIW, if you want only those rows where the second part after the semicolon exactly equals "ABC" (ignoring whitespace), then I believe something like this might work (untested)

Select * From dbo.myTable 
    Where 
        Replace( 
            SubString( 
                myField, CharIndex(';',myField), Len(myField)
                ), 
            ' ','' 
            ) = ';ABC';

Regards
-Stefan