Isophorone diamine (CAS No. 2855-13-2) was evaluated for subchronic inhalation toxicity in male rats (10/dosage group, breed unspecified) administered whole-body exposures to nominal aerosol/vapor concentrations of 18, 200, and 550 mg/m3, 6 hours/day for 9, 9, and 4 days, respectively. Following 9 exposures, 5 rats from each group (surviving numbers allowing) were sacrificed and necropsied, while the remaining were sacrificed after a subsequent 20-day recovery period. Treatment with 550 mg/m3 was associated with significantly reduced bodyweights and mean bodyweight gains and mortality (4/10) by completion of a fourth exposure, such that all surviving rats (6/10) of this group were sacrificed and necropsied with decedents following the fourth exposure. Dose-dependent histopathology was identified in the nose (18, 200, 550 mg/m3), trachea (200, 550 mg/m3), larynx (200, 500 mg/m3), and lungs (200, 550 mg/m3). Necrosis as well as hypertrophy/hyperplasia noted in the lungs and trachea of 4-day 550 mg/m3 rats and 9-day rats appeared resolved after 20-day recovery, as tissue repair was also apparent in the nose and larynx of these animals. The study report is summarized only and no further data are provided.