Twenty-five mild and 19 severe preeclampsia cases in twin pregnancies (12.5%) were compared to 44 matched for gestational age controls. All three groups were similar with respect to maternal age, intertwin birthweight differences, and rates of abdominal deliveries and low (less than 7) 5-minute Apgar scores. The frequency of primiparas in the severe preeclampsia group was significantly higher compared with controls (p less than 0.03). Severe preeclampsia patients delivered at a significantly earlier gestational age (p less than 0.005) and had a significantly lower mean twin birthweight (p less than 0.003) compared with the mild preeclamptic group. The mean twin birthweight of the severe preeclamptic cases was also significantly lower compared with that of controls. All three neonatal deaths occurred in severely discordant second twins born to severe preeclamptic patients. It is concluded that adverse perinatal outcome is associated with severe but not with mild preeclampsia in twin gestations.