Three recent investigations are based on mean values of dry-bulb temperature and vapour pressure for four stations: London Airport, Plymouth, Tyne mouth, and Manchester. Using weekly values for the years 1947-1952 inclusive, Bradley and Richmond (1953) concluded that there was a tendency for lower average seasonal temperature/vapour pressure to occur with the lowest incidences of poliomyelitis. From a study of these temperature data, Lawrence (1956) showed that incidence was highly correlated with "accumulated" temperature above a threshold temperature. Using monthly averages for the years 1947-1956 inclusive, Spicer (1959) obtained strong positive correlations with temperature and negative correlations with relative humidity, but "found that vapour pressure was not related to the incidence of poliomyelitis". However, Spicer states that his ana lysis does not exclude the possibility that other meteorological variables, closely related to tempera ture and relative humidity, may be involved.