Acute inhalation toxicity was evaluated in a single group of 10 Sprague-Dawley rats (5 male and 5 female) exposed to benzenesulfonyl chloride at a measured concentration of 1.87 mg/l for 1 hour. Mortality was observed in 9 animals during the 14 day observation period, and an LD50 value was not reported. Clinical observations included reduced activity, wet muzzles, dyspnea/wheezing, dacryorrhea, chromodacryorrhea, chromorhinorrhea, brown flecks on chin and face, wet pelvic/ventral areas, and some hair loss. Gross necropsy revealed pulmonary congestion, reddened lungs (which failed to collapse in several animals), stippled red thymus, and gas distended stomachs.