Drug Use in Pregnancy (DUP) is an international epidemiological survey of drug use in pregnancy conducted from 1988 to 1990 in 148 maternity wards, representing the general delivery practices of 22 countries. Data on exposure of pregnant women to psychotropic drugs, the indications for their use and their correlation with maternal characteristics are reported. Of the 14,778 women interviewed, 520 (3.5%) reported 562 courses of psychotropic drugs. Benzodiazepines (BDZ) accounted for the greatest number of the exposures (444/520 women); neuroleptics and antidepressants were prescribed to tiny minorities of women (83 and 17 respectively), mostly in those few countries were the overall prevalence of use of those drugs was highest. Throughout the majority of the other countries, overall rates were in the low range and were rather heterogeneous. With the exception of small clusters of "unexpected" indications, prescriptions of BDZ were found to be consistent with the target symptoms of anxiety and insomnia; chronic use was reported in 31/444 women. The study was not targeted to the detection of malformations; no suspected clustering was found, however, among the 130 women exposed during the first trimester of pregnancy. The collaborative network now established provides a framework for periodically replicated surveillance to monitor the evolution of this field of knowledge and care in order to provide reliable information for women and society.