The purpose of this study was to evaluate the teratogenic potential of mefloquine (Lariam) in pregnancy, based on the Roche International Spontaneous Reporting System. Lariam is an anti-malarial drug used both in prophylaxis and treatment of malaria. Teratogenic effects were observed in animals but data from humans are lacking. Women of childbearing potential are currently advised to take contraceptive precautions up to three months after the last dose. The study included 1,627 spontaneous reports of women exposed to Lariam before or during pregnancy, which were received by Roche worldwide since introduction on the market. The data were analyzed considering pregnancy and fetal outcome and type of congenital malformations. The birth prevalence of congenital malformations in women exposed to Lariam is estimated to be 4% and is not different from the prevalence observed in the general population. In addition, the congenital malformations observed with Lariam exposure do not show any specific pattern. The data from our study suggest that the teratogenicity, which was observed in animals at high doses, cannot be applied to humans.