The population of the sugar estates of the Guyana coastlands was 110 000 in 1966; malaria was eradicated between 1945 and 1951. A study has been made of the pattern of mortality before and after malaria eradication, during the 30-year period from 1937 to 1966.The decline in general mortality has greatly exceeded the fall in mortality specifically related to malaria and has continued for almost 10 years after registration of the last death from malaria. In infants, mortality has been reduced, mainly through a decline in the number of deaths from prematurity and congenital debility that were due mainly to malaria and its sequelae in the expectant mother. In children (1-14 years of age) the decline has resulted from the disappearance of malaria and chronic nephritis as causes of death. In adults, mortality has fallen mainly through the progressive decline in the incidence of a number of diseases not overtly related to malaria: acute and chronic respiratory diseases, chronic nephritis, and the anaemias. Cardiovascular diseases, on the contrary, have shown a tendency to increase since malaria was brought under control.