The potential maternal toxicity and developmental toxicity of Pyrazole were evaluated. Pyrazole was suspended in Mazola corn oil and administered to four groups of eight bred Sprague Dawley Crl:CD(trademark)BR rats once daily from gestation days 6 through 18. Dosage levels of 25, 100, 175 and 225 mg/kg/day were administered at a dose volume of 5 ml/kg. A concurrent control group, composed of eight bred females, received the Mazola corn oil vehicle on a comparable regimen at 5 ml/kg. The route of administration was oral by gastric intubation. Throughout gestation all rats were observed at least twice daily for appearance and behavior. Body weights were recorded at appropriate intervals. All surviving animals were sacrificed on gestation day 20 for a scheduled Cesarean section. The uteri and ovaries were examined and the number of fetuses, early and late resorptions, total implantations and corpora lutea were recorded. The thyroid glands, kidneys, spleen and liver of each female were weighed. The thyroid glands were retained for possible future examination. The fetuses were weighed, sexed and examined for external malformation and developmental variations, and discarded.