Gastroschisis, which is a defect in the abdominal wall, lateral to the umbilical cord, is considered to be a vascular problem, probably due to a disruption of the omphalomesenteric artery [Hoyme et al. (1981) J. Pediatr. 98:228-231]. Recently, Torfs et al. [(1996) Teratology 54:84-92] observed a significantly increased risk for aspirin and ibuprofen, two strong cyclooxygenase inhibitors. Here we present the results of a case-control study conducted by the Spanish Collaborative Study of Congenital Malformations (ECEMC) on the relationship between prenatal exposure to salicylates during the first trimester of pregnancy and gastroschisis. The results show an increased risk (OR = 3.47; P = 0.015) after controlling the possible effect of maternal age and maternal smoking during pregnancy.