Respiratory distress syndrome (RDS) is the major cause of morbidity and mortality in preterm twin deliveries. Therapy with corticosteroids has been shown to reduce the incidence of RDS in preterm singleton gestations but similar reductions in twin pregnancies have not been demonstrated. Maternal and neonatal medical records were reviewed from twins delivered between 24 to 34 weeks gestation over the period of January 1, 1990 to December 31, 1994. Twenty-one pairs of twins received optimal steroid treatment defined as the use of two 12 mg doses of betamethasone, with birth occurring between 24 hours and 7 days after the first dose. Sixty-three pairs received no treatment. The mean gestational age at delivery was 29.9 +/- 2.6 weeks. No decrease was seen in the incidence of RDS (optimal steroid 70.7% versus no treatment 68.0%, unadjusted odds ratio [OR] 1.14, 95% confidence interval [CI] 0.49 to 2.65). Multivariate logistic regression showed no statistical difference in the incidence of RDS in the optimal steroid compared to the no treatment group (adjusted OR 0.63, 95% CI 0.2 to 1.95). No statistical differences were noted in the incidence of mechanical ventilation (58.6% versus 55.4%, p = 0.83), median duration of intubation (5.0 versus 5.0 days, p = 0.47), the median maximum inspiratory pressure requirements (20.0 versus 22.0 mm Hg; p = 0.15) in the optimal treatment versus no treatment group, respectively. The current regimen of antenatal corticosteroids utilized in twin pregnancies does not reduce the incidence of RDS.