Thanks for replying. I've tried via the UI by unticking them from the article, i've tried RMO using the example here (http://msdn.microsoft.com/en-us/library/microsoft.sqlserver.replication.transarticle.removereplicatedcolumns.aspx) and the sp_articlecolumn sproc. All essentially do the same.

Previously the columns were in a separate unreplicated table but due to performance problems caused by joining 100,000's rows together and index fragmentation i'm trying to move them into the same table.