The prevalence of autoantibodies in B cell chronic lymphocytic leukaemia (B-CLL) was investigated. A lower prevalence of autoimmune haemolytic anaemia than that found in other series was found: large numbers of non-progressive stage A disease cases were included, in which the prevalence of autoimmune haemolytic anaemia is low. Non-haematological autoantibodies were no commoner than in age matched controls. Whatever explanation is offered for autoimmune phenomena in B-CLL it must take account of the fact that those phenomena are virtually confined to autoantibodies against the formed elements of the blood.