n order to evaluate the carbohydrate metabolic effects of certain drug therapies used in treating the toxemia syndrome, 75 term pregnant women were studied with two intravenous glucose tolerance tests performed 1 week apart. During the 2-hour tests, both blood glucose and plasma insulin were measured. The women were randomly assigned to three treatment groups, and during the week between the tests they received: a) no drugs (control or C group); b) Diuril®,500 mg/day (D group); or r) Dilantin®, 100 mg,. i.d. (DL group). Each group was of similar age, weight, and gestational age. There were no significant changes in any of the glucose curves. Both drug-treated groups demonstrated insulin changes. In contrast to the C group, the D group -showed an elevation of the plasma insulin values during the second test, and the DL group had a lowering of plasma insulin levels in the second test. Thus, both drugs had minor effects on carbohydrate metabolism during short-term use. However,: i more marked metabolic effect of these drugs must be considered when using them at higher dosages or for a longer duration.