The European Network of the Teratology Information Services (ENTIS) has collected and evaluated data on 689 pregnancies in which exposure to tricyclic and nontricyclic antidepressants occurred. Data were collected prospectively from the time of in utero exposure and all the cases were followed up to the first few weeks of postnatal life using standardized procedures. In most cases, no longer term follow-up data were available. Approximately two-thirds of the mothers were on multidrug therapy, and of those, half took a benzodiazepine. About 95% of the patients were exposed during the first trimester. The most striking feature of the pregnancy outcomes is that 97% of live-born babies were morphologically normal. The incidence of spontaneous abortion and late fetal/neonatal deaths were within the normal range. Fourteen live-born babies and one fetus had either major or minor malformations, and six had minor anomalies. However, there was no increase in either a particular type of malformation or a specific pattern of defects. Another 31 infants without malformations had neonatal problems; these were usually associated with chronic multidrug therapy, especially near term. Elective termination of pregnancy occurred more frequently in the multidrug groups (86 out of 488) than in the monotherapy groups (20 out of 201), but data concerning the condition of the fetus are not available in the majority of the cases. Overall, no causal relationship could be established between in utero exposure to antidepressants and adverse pregnancy outcome.