Aniline (62-53-3) was evaluated for acute inhalation toxicity in Crl:CD rats administered single nose-only or whole-body vapor exposures. By contrasting means of exposure, the study authors also sought evidence that incidental dermal toxicity in whole-body exposures or stress associated with restraint for nose-only exposures contributed to mortality. Single whole-body aniline vapor/aerosol exposures at mean concentrations of 359, 400, 453, 530, and 786 ppm (O2 levels maintained at 21%), each administered to groups of 10 male Crl:CD rats for 4 hours, produced mortality consistent with an LC50 (with 95% confidence limits) of 478 (442-540) ppm. All but 1 lethality occurred on Days 0 or 1 of 14-day post-exposure observation. By contrast, the mortality in groups of 10 rats restrained for 4-hour nose-only exposures to concentrations of 681, 790, 834, and 896 ppm yielded an inhalation LC50 of 839 (802-882) ppm. All decedents of nose-only exposures died during the 2 days following exposure, except one rat of the high concentration which died on post-exposure Day 4. During treatment, cyanosis, tremors, and prostration characterized all exposures, regardless of the level or mode of delivery, and transient weight loss characterized all post-exposure observations. Nose-only exposures, however, also induced immediate signs of persisting ocular and nasal irritation including corneal clouding, reddish-brown nasal discharge, chromodacryorrhea, and lacrimation. Corneal clouding induced during nose-only exposures either persisted or worsened to mild-severe damage over 14-day post- exposure observation, while loss of head and facial hair occurred late and persisted throughout observation in survivors of 400-453 ppm whole-body exposures. The wide LC50 discrepancy associated with method of exposure was attributed to aniline dermal absorption and toxicity upon whole-body exposures to the vapor/aerosol.