The observed incidence of sudden infant death syndrome (SIDS) in Hillsborough County is significantly higher than corrected rates in three other metropolitan areas of the state which have common demographic features. An eight year analysis of data (1979-1986) demonstrates the consistency of the observation. Since SIDS is a postmortem diagnosis of exclusion utilized for deaths of infants for whom no anatomic or biochemical cause can be determined and represents a large segment of deaths between 28 days and one year of age, there is a need to assure that all areas of the state utilize similar criteria for assignment of the diagnosis.