Male and female Sprague-Dawley (SD) rats were exposed to concentrations of 0, 500, 1500, or 3000 ppm of n-butyl acetate for 6 hours per day, S days per week for 13 consecutive weeks. The time-weighted average analytical concentrations were within 10% of the target concentrations. The daily mean temperatures and relative humidity inside the chambers during exposure were 21.1 - 24.7*C and 36.7 - 68.7%, respectively. No spontaneous mortality occurred during the study. Animals were observed for signs of toxicity prior to exposure, once per hour during exposure, and 30 minutes to one hour after exposure. Animals exposed to 3000 ppm had reduced activity levels which were of generally minor severity during exposure. Signs of slalarzhea and red discoloration on the chin hair were also observed. Animals exposed to 1500 ppm exhibited reduced activity of generally minimal severity. Control and 500 ppm animals appeared normal during exposure. After exposure, animals in all groups had porphyzin nasal discharges and dried porphyrin stains around the nose. These clinical signs were occasionally seen during the morning examination before exposure. Mean body weights for the 3000 ppm group were significantly (ps 0.05) lower than the control group for male rats on Days 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, and 91, and for female rats on Days 14, 21, 28, 35, 42, 56, 63, 70, 77, 84, and 91. Mean feed consumption for the 3000 ppm groups were significantly lower (ps 0.05) than for the control group throughout the study for male rats and at all intervals except Days 84 and 91 for female rats. Mean body weights for the male 1500 ppm group were significantly (ps 0.05) lower than the control group on Days 42, 49, 56, 63, 70, 77, 84, and 91. Mean body weights for the female 1500 ppm group were significantly (ps 0.05) lower than the control group on Days 14, 21, 28, 35, 42, 56, 63, 70, 77, 84, and 91. Mean feed consumption values for the 1500 ppm groups were significantly lower (ps 0.05) than for the control group on Days 35, 42, 49, 56, 63, 70, 77, and 84 for male rats and at all intervals except Day 91 the female rats. Idean body weights for the 500 ppm groups,were comparable to the control group throughout the study, and no statistically significant differences were noted. However, mean feed consumption values for the 500 ppm groups were significantly lower (p 5 0.05) than for the control group on Days 35, 42, 63, and 70, for male rats and on Days 7 and 14 for female rats.