Objective: To assess the risk of vaginal birth of breech first twins by Apgar scores and mortality.Methods: We did a retrospective case-control analysis of data from 13 centers that allow vaginal birth for breech first twins. We used depressed 5-minute Apgar scores and neonatal mortality as main outcome measures between vaginal (n = 239) and cesarean (n = 374) deliveries of pairs with breech first twins, stratified by parity, birth weights of first twins, and types of cesarean. The 95% power of our sample size (α = .05) was sensitive enough to detect differences of 5% of the overall sample and 25-30% of subgroups.Results: Vaginal birth was attempted in 61% of 613 pairs. There were significantly more depressed Apgar scores (P = .008, odds ratio [OR] 2.4, 95% confidence interval [CI] 1.2, 4.7) and neonatal deaths (P < .001, OR 9.5, 95% CI 4.0, 23.4) among vaginal births of pairs in whom first twins weighed less than 1500 g but not among the higher-birth-weight cohort (for depressed Apgar scores: P = .76, OR 1.1, 95% CI 0.6, 2.1). Multiparity and elective cesarean seemed to have little influence on outcome measures. Neonatal mortality was associated with extremely preterm twins.Conclusion: There was no evidence that vaginal birth is unsafe, in terms of depressed Apgar scores and neonatal mortality, for breech first twins that weighed at least 1500 g. Copyright (C) 2000 The American College of Obstetricians and Gynecologists.