Since the last war it has become widely recognized that the low incidence of paralytic poliomyelitis in under developed countries is associated with an actual hyperendemicity of the disease in those regions. This hyperendemic state is revealed by the sporadic occurrence of cases of infantile paralysis and by the immune state of virtually the whole of the native population over the age of 5. The actual number of these sporadic cases is much greater than has often been realized in the past, owing to poor reporting. Quite a number of cases have also been diagnosed as sciatic palsies following the injection of quinine for fever. This infantile pattern of infection appears to have been almost world-wide until approximately 1870 ; since then two distinct changes have been noted, beginning in the more highly developed countries. In the first phase, epidemics of the paralytic disease occurred, still confined to those under 5 and apparently unrelated to the season ; in the second phase the age incidence steadily increased, there was a marked increase in the severity of the disease, and it tended to become seasonal. The epidemic described below falls into the first phase of this change? that is, there was a sudden very high incidence of paralytic disease without any alteration in age incidence.