Objective: The purpose of this study was to identify the success rates and risks in women with a twin pregnancy who attempt a trial of labor after cesarean delivery. Study design: Cases were identified in the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network's Cesarean Registry with a woman with a twin pregnancy who had had at least 1 previous cesarean delivery. Results: During the study period (1999-2002), 412 women fulfilled the study criteria, and 226 women had elective repeat cesarean delivery. Of the 186 women (45.1% of total) who attempted a trial of labor, 120 women were delivered successfully (success rate, 64.5%), and 66 women (35.5%) had a failed trial of labor. Thirty of the failed trials of labor involved a vaginal delivery for twin A and cesarean delivery for twin B. Women who attempted a trial of labor with twins had no increased risk of transfusion, endometritis, intensive care unit admissions, or uterine rupture when compared with elective repeat cesarean delivery. Fetal and neonatal complications were uncommon in either group at ≥34 weeks of gestation. Conclusion: A trial of labor with twins after previous cesarean delivery does not appear to increase maternal morbidity. Perinatal morbidity is uncommon at ≥34 weeks of gestation. © 2005 Mosby, Inc. All rights reserved.