N-Methylpyrrolidone (872-50-4) was evaluated in a dose range-finding teratology study in which groups of 5 female Sprague-Dawley rats were administered the test substance dermally applied to the back at 0, 0.5, 1.1, or 2.5 g/kg/day on days 6 through 15 of gestation. Animals were sacrificed on da 20 of gestation. Animals in all test levels had dry patches of skin on the backs and showed bright yellow urine. Four out of 5 animals at the 2.5 g/kg/day group died. Maternal body weight gain was decreased at 1.1 g/kg/day but was not affected at 0.5 g/kg/day. At 1.1 g/kg/day 65/66 fetuses were resorbed (the single surviving fetus wassignificantly smaller than control fetuses). There was no effects on pregnancy, implantation, or gestation in the 0.5 g/kg/day group when compared with controls. None of the fetuses from treated dams at any level exhibited external abnormalities or malformations. Significance was judged at a probability level of 0.05 in all cases.