Both a subchronic inhalation study and a developmental toxicity screen were performed with vapors of light catalytically cracked naphtha (LCCN). In the subchronic study, four groups of mice and rats (10 animals per sex per species) were exposed for approximately 13 wk (6 h/d, 5 d/wk) to concentrations of LCCN vapors of 0, 530, 2060, or 7690 mg/m3. An untreated control group was also included. Animals were observed daily and body weights were taken weekly. No significant treatment-related changes were found in clinical signs, body weight, serum chemistry, hematology, histopathology of 24 tissues, or weights of 12 organs. A marginal decrease was noted in the number of sperm per gram of epididymis. In the developmental toxicity screen, presumed-pregnant Sprague-Dawley rats were exposed to 0, 2150, or 7660 mg/m3 of LCCN vapors, 6 h/d on d 0-19 of gestation. Females were sacrificed on d 20; dams and fetuses were examined grossly and fetuses were later evaluated for skeletal and visceral effects. The number of resorptions was increased by ~140% in the group receiving 7660 mg/m3; no other definite treatment-related changes were observed. Overall, the effects of exposure to partially vaporized LCCN were minimal.