Phenyl isocyanate was tested for acute inhalation toxicity with albino rats (4/sex/group) exposed for 1 hour to concentrations of up to 80 ppm (values not reported) of vapor generated by bubbling air through liquid test chemical. Summary information indicates the LC50 was 12.6 ppm (95% confidence limits = 8.4 to 19.0 ppm). Subchronic assays were conducted with albino rats (8/sex/group) exposed to 0, 0.055, or 0.496 ppm test material for 6 hours/day, 5 days/week for a total of 15 exposures. Results of histopathological analysis were not yet completed. Low-dose rats showed lung effects (increased resistance at the end of the 3rd week of exposure), and high dose animals had decreased tidal volume, rate, minute volume and compliance, and increased resistance on days 11 and 12. Other effects seen in high-dose rats included reduced body weight by day 12, evidence of hemoconcentration, and death or moribundity. A no-effect level was not identified.