SUMMARYBiosynthetically labelled Qa‐2 antigens were isolated from mouse spleen cells by immunoprecipitation with anti‐Qa‐2 antisera. When newly synthesized Qa‐2 molecules from several different inbred strains were analysed by two‐dimensional (2D) gel electrophoresis; four different phenotypes were observed that differed in the number of polypeptides present. The ability to distinguish Qa‐2+phenotypes was used to map the recombination points in two congenic strains, B6.TlaaandA. Tlab. No alternative Qa‐2‐like polypeptides were detected in B6.K1 (Qa‐2−) cells using a polyspecific rabbit antiserum against mouse class I antigens, but a new molecule was detected in BALB/cBy (Qa‐2−) cells. Pulse‐chase and surface‐labelling experiments showed that some, but not all, of the newly synthesized Qa‐2 precursor forms are processed to