The authors report a humoral immunity study in 39 black Nigerian women with peripartum cardiomyopathy. Serum immunoglobulins (IgG, IgA, IgM) assay, evaluation of serum immune complexes (immunonephelemetric method) and of heart muscle autoantibodies (indirect immunofluorescent double layer technique in heart muscle of the rat) were made. Forty breastfeeding black Nigerian women without cardiac disease were the controls. Differences between serum immunoglobulins, circulating immune complexes and heart muscle autoantibodies are not significant. This study demonstrates the absence of a humoral autoimmunity process in peripartum cardiomyopathy.