OTTO Fuel II (OFII) is a propellent used by the United States Navy in its Mk 46 and Mk 48 torpedoes. Owing to the possibility of human exposure during fueling and defueling operations, studies were initiated to determine if OFII was a developmental toxin. Phase I of the investigation involved dosing four groups of time-mated Fischer-344 rats with OFII. The fuel was administered dermally at the rate of 0, 400, 2000 and 4000 mg/kg/day. A significant reduction in body weight was seen at necropsy in dams receiving 2000 and 4000 mg/kg/day of OFII. Fetuses from these dams also weighed significantly less than control fetuses. Phase II of the investigation involved dosing of artificially inseminated rabbits with OFII. The fuel was administered to the skin of the animal's back at the rate of 0, 100, 316 and 1000 mg/kg/day. Maternal toxicity was evidenced by a significant reduction in body weight of the dams in the 1000 mg/kg/day dose group on days 20 and 25 of gestation. There were no significant differences observed in maternal weight or fetal weight at necropsy. Morphological examination of both rat and rabbit fetuses faded to reveal significant evidence of fetal malformations. OTTO Fuel II, Teratology, Rat, Rabbit, Propylene Glycol Dinitrate (PGDN).