Phenyl isocyanate (CAS No. 103-71-9) was evaluated for subacute inhalation toxicity. The test substance was administered to albino rats (8/sex/group) exposed to air (control), petroleum ether (control), or 0.5 ppm or 0.05 ppm phenyl isocyanate for six hours a day for 14 days. The test atmosphere was generated from a Hamilton syringe placed in a sage pump diluted in petroleum ether. In the group exposed to 0.5 ppm, mortality was observed in one male rat on day 9 and one female rat on day 11. Clinical observations revealed no abnormalities in air control, petroleum ether control, or 0.05 ppm animals. Animals exposed to 0.5 ppm showed signs of severe respiratory distress with nasal discharge, piloerection, and reparative epithelial hyperplasia in the bronchi and bronchioli accompanied by polyp formation and submucosal obstructive fibrosis. Gross necropsy revealed marked and extensive reddened areas/foci in a few animals exposed to 0.05 ppm or petroleum ether. Gross examination findings for animals exposed to 0.5 ppm included inflated lungs in 6 males and 2 females, pale lungs in 2 males and 2 females, and superficial red areas/spots in 7 males and 6 females.