Trends in postperinatal infant mortality from respiratory causes and the sudden infant death syndrome in England and Wales for 1968 to 1984 were examined. These were compared by time series analysis with changes in the incidence of specific infective diseases and organisms for the same period. Discontinuity was found in association with the occurrence of whooping cough between 1977 and 1982. Associations with the general incidence of respiratory infections and other specific organisms were less evident. An estimate of excess mortality is 460 to 700 deaths, a substantial increase over the certified mortality from whooping cough.