N-isopropylaniline (CAS No. 768-52-5) was evaluated for acute inhalation toxicity in groups of Sprague-Dawley rats (5/sex/group) exposed for 4 hours in an inhalation chamber to mean analytical concentrations of 1.4, 1.4, 1.3, 1.0 mg/L vapor/aerosol in air. Mortality associated with treatment was consistent with an LC50 (probit) of 1.2 mg/L in air. Rats of a 1.0 mg/L exposure showed neither overt signs of toxicity nor diminished weight gain, while all other treated groups exhibited a transient decrease in mean bodyweights on Day 2 following exposures. Hypoactivity and respiratory distress or irritation were the most oft reported clinical irregularities during 14-day post-exposure observation. Necropsy of both surviving and decedent rats revealed no treatment-related pathology.