IN 1965, Melzack and I proposed a gate control theory and later we modified and modernized the original proposal (Melzack, 1973; Wall, 1973, 1974, 1976). Nathan (1976) has written a detailed review in which he concentrates particularly on mechanisms. Here I would like to extend his review to show where new knowledge requires a modification of our previous thinking, where the theory stands now and where gaps in our knowledge still prevent movement from speculation to reality. There were certain points in our original statement which seem to have been misunderstood and these need clarification. The diagram of mechanism we published had all the disadvantages of excessive clarity with its emphasis on the substantia gelatinosa and presynaptic mechanisms. The body of the paper mentioned other possible mechanisms but it has seemed to some that the entire theory rested on the diagrammatic mechanism which we shall see is not the case. Of course there have been many interesting discoveries since 1965 which need reviewing. X Some of these new facts show that the data on which some of the theory was based was frankly misleading. Finally we shall try to show where the persistent inadequacy of technique still prevents an elucidation of mechanism.