A collaborative study with 8 Teratology Information Centres was undertaken to collect data on anorectic exposures (amfepramone, clobenzorex, dexfenfluramine, fenfluramine, fenproporex) during pregnancy. Two hundred and ninety seven prospective enquiries were analysed of which 285 exposures occurred during the first trimester. Outcome of pregnancy was known for 164 of these cases. Voluntary or medical abortion was decided in 30 cases (18%), spontaneous abortion occurred in 14 cases (8.5%), extrauterine pregnancy in 1 patient and fetal death following drug abuse in another. A normal infant was delivered in 111 cases (68%). Low birthweight was identified in 1 case and neonatal complications in 2 cases. Various congenital abnormalities were noted in 4 cases (1 minor and 3 major), with no clear cause-effect relationship (2 amfepramone, 1 fenproporex and 1 dexfenfluramine). Although the number of exposed pregnancies in this cohort was too small to rule out any increase in teratogenic effects of anorectics, the results of this survey suggest that the risk for malformations, especially for dexfenfluramine is probably not greater than the 2-3% risk for pregnancies in the general population. Morover, these results provide substantial information for future enquiries about exposure to such medication during organogenesis.