Major differences in personality structure between obsessional neurotics and their relatives are against the hypothesis that there is a strong genetic component in obsessional states. Analysis of symptom patterns contradict a major role for aggression, either overt or controlled, in this condition. Anxiety of endogenous origin is seen as the major basic cause and obsessional symptoms act as defences against mounting pathological anxiety. This process needs to be studied more closely if rational treatment is to eventuate.