Pregnant Sprague-Dawley rats were exposed to 0, 400, 1000 or 3,000 ppm methyl ethyl ketone (MEK) on day 6 through 15 of gestation. Maternal toxicity, as evidenced by decreased weight gain and increased water consumption, was observed among rats exposed to 3,000 ppm MEK. Slight fetotoxicity was observed as evidenced by an increased incidence of some minor skeletal variants among litters from animals exposed to 3,000 ppm MEK. No embryotoxic effects were observed. Although a slight fetotoxic effect and slight maternal toxicity were observed at the highest exposure level, MEK was not embryo-toxic or teratogenic in rats at exposure levels up to 3,000 ppm.