An omphalopagus set of female conjoined twins, undiagnosed prenatally, who presented as obstructed labour needing operative delivery is reported. Their anatomic characteristics and clinical features, including overwhelming sepsis in twin II which forced early separation, and those which led to their demise are described. Twelve other cases reported in Nigeria over the past 60 years are reviewed with reference to the aetiology and epidemiology of conjoined twinning and the determinants of successful surgical separation.