A 90-day inhalation toxicity study using B (sub 6) C (sub 3) F (sub 1) mice, Sprague-Dawley (CD) rats and Fischer-344 (CDF) rats (exposed simultaneously in the same chambers) was conducted with hydrogen chloride gas. Three groups, each consisting of 31 males and 21 females of each species/strain, were designated as groups T-I, T-II and T-III and exposed to atmospheres of hydrogen chloride as target concentrations of 10 ppm, 20 ppm, and 50 ppm, respectively. After the fourth exposure, 15 males and females per group per species/strain were sacrificed. In addition, a control group (UC) consisting of 31 males and 21 females of each species/strain was exposed to clean air only and was handled in a manner similar to that of the test animals. The duration of exposure was 6 hours per day, 5 days per week for 90 days. Initial exposures for interim sacrifice animals and each species/strain were staggered to accommodate necropsy scheduling.