By record-linkage of the 1975 Swedish census and the Medical Birth Register of infants born in 1976, 1,161 infants were identified who were born to women coded as laboratory workers in the census. These infants were compared to all 98,354 infants born in Sweden in 1976. There was a higher than expected number of infants who died neonatally and/or had congenital malformations. Twenty-six singleton infants who either died or had serious malformations were selected for further study. To each of the cases, 2 controls were selected among the 1,161 infants. A questionnaire was sent to the 26 cases and 50 controls (2 cases had only 1 control each) asking about work during pregnancy. No specific type of laboratory work was found to be more common among the cases than controls.