Abstract: A shirt construction includes an adjustable collar for accommodating different neck sizes, and an adaptor is operable in combination with a conventional shirt for adapting the collar thereof for adjustability. The shirt construction includes an extension tab which extends from a first front edge portion of the shirt adjacent the collar thereof, a reinforcing panel for reinforcing the first front edge portion and hook-and-pile-type fastening elements for adjustably securing the first front edge portion to an opposite second front edge portion adjacent the shirt collar. The adaptor includes an extension tab and a reinforcing panel which are securable to buttons on a first front edge portion of a shirt adjacent the collar thereof, a fastening tab which is securable in a collar buttonhole of a second front edge portion of the shirt, and a hook-and-pile-type fastening element for adjustably securing the extension tab to the fastening tab.