Sernyl, 1 aryl-cyclo-hexylamine, is a synthetic drug first used by the anaesthetists because, when given intravenously, it produces analgesia. However, the occurrence of psychological disturbances post-operatively led to the investigation of this drug by psychiatrists. It was found that Sernyl produces many interesting psychological disturbances, some of which resemble the primary symptoms of schizophrenia (Davies and Beech, 1960). In a previous paper (Davies, 1960) Sernyl was given intravenously to five patients with long-standing psychoneurotic illnesses. It proved to be an effective abreactive agent and produced some interesting results in three of the patients who had obsessional symptoms. Sernyl, in the doses used, is not an hallucinogen, though it produces other effects similar to lysergic acid diethylamide, which has been used extensively as a therapeutic agent, particularly in obsessional states (Sandison et al., 1954). The preliminary report suggested that Sernyl might have some practical advantages over LSD—in particular, it produced a less severe disturbance and its effects were over more quickly. Further investigations were clearly indicated and this present paper reports on the use of oral Sernyl in five patients with obsessional illnesses.