Sulfur mustard (SM), a vessicating agent, has been used in chemical warfare since 1918. The purpose of this study was to quantitate SM vapor deposition, tissue distribution, and excretion following intratracheal inhalation in rats and cutaneous exposure in guinea pigs. 14C-SM vapors for inhalation studies were generated by metering liquid 14C-SM into a heated J tube. Vapors were transported via carrier air supplemented with oxygen and isoflurane to an exposure plenum. Anesthetized rats with transorally placed tracheal catheters were connected to the plenum port via the catheter hub for exposure (approximately 250 mg 14C-SM vapor/m(3); 10 min). For dermal exposure, 3 Teflon cups (6.6 cm(2) exposure area per cup) were applied to the backs of each animal and vapors (525 mg 14C-SM/m(3); 12 min) were generated by applying 6 μl 14C-SM to filter paper within each cup. Animals were euthanized at selected times up to 7 d postexposure. SM equivalents deposited in rats and guinea pigs were 18.1 ± 3 μg and 29.8 ± 5.31 μg, respectively. Inhaled SM equivalents rapidly distributed throughout the body within 2 h postexposure, with the majority (>70%) of material at that time located in carcass and pelt. In guinea pigs, >90% of deposited SM equivalents remained in skin, with minor distribution to blood and kidneys. Urine was the primary route of excretion for both species. Results indicate inhaled SM is rapidly absorbed from the lung and distributed throughout the body while there is limited systemic distribution following cutaneous exposure.