To evaluate the influence of rate of gestational weight gain on newborn birthweight and birthlength in twin gestations complicated by preeclampsia, 74 cases of preeclampsia in twin pregnancy were matched to 148 non-preeclamptic twin controls for maternal race, height, pregravid weight, age and length of gestation. Total weight gain was significantly higher for all cases versus controls and for mild cases versus controls. However, the rate of early weight gain was lower for severe cases and severe cases with thrombocytopenia compared to their controls. Mean birthweight and birthlength did not differ between cases and controls, although the proportion with birthlength below the 10th percentile was significantly higher among cases than controls. In addition, the proportion of birthweights and birthlengths < 10th percentile was significantly higher among cases than controls. These findings suggest that inadequate early weight gain in twin gestations complicated by preeclampsia results in retarded birthlength and birthweight. The implication of these findings are discussed.