We sought to determine whether early amniocentesis is a safe and acceptable method of genetic evaluation in early pregnancy. During the 54-month period from September 1986 to February 1991, 300 consecutive early second-trimester amniocenteses were performed transabdominally at 13-14 weeks' gestation and 567 consecutive mid-second-trimester transabdominal amniocenteses were performed at 16-18 weeks. Group assignment was nonrandomized, interoperator-dependent variables were eliminated, and analysis was performed in one cytogenetics laboratory. The median maternal age and indications for the procedure were similar in both groups. There were no significant differences between the early- and mid-second-trimester amniocenteses in failed sampling, ambiguous results, pregnancy loss from 4 weeks after the procedure to 28 weeks' gestation, preterm birth, or perinatal death rate. Pregnancy loss within 4 weeks of amniocentesis was more frequent in early- than in mid-second-trimester amniocenteses. We conclude that early amniocentesis is a safe and acceptable method of genetic evaluation.