Oligomeric condensation products of certain dialdehydes and phenols can be end-capped with a vinylbenzyl moiety and certain other moieties, especially alkyl groups, to afford thermosetting resins particularly valuable in making laminated circuit boards. Resins prepared by the reaction of 1 molar proportion of glyoxal with from 3 to 4 molar proportions of phenol and end-capped with from 50 to 85% vinylbenzyl groups with the remainder being alkyls of 1 through 11 carbon atoms are particularly useful.