In a case-base study among 214,108 commercial and clerical employees in Denmark the potential effect of the use of video display terminals on the risk of congenital malformations in pregnancy was investigated. The study base was identified by means of register linkage of the Medical Birth Register and the National Register of In-Patients. In the source population 24,352 pregnancy outcomes were registered, 661 of which with congenital malformations entered the case group, and a base sample of 2252 pregnancies was drawn. Data concerning the use of video display terminals, job stress, ergonomic factors, exposure to organic solvents, and life-style factors were obtained from postal questionnaires. The results of this study did not support the hypothesis that the use of video display terminals during pregnancy is associated with an increased risk of congenital malformations.