Male and female Sprague-Dawley rats and New Zealand White rabbits were exposed to 0, 30, 100 or 300 ppm ethylene glycol monomethyl ether (EGME) vapors 6 hours per day, 5 days per week, for a total of 13 weeks. No rats died prior to scheduled sacrifice, but some rabbits in the 100 and 300 ppm exposure groups died or were sacrificed when moribund during the study. Body weights as well as thymus and testicular weights of rats and rabbits in the 300 ppm group were reduced as a result of the exposures. Hematologic changes occurred in rats and rabbits exposed to 300 ppm. Concentrations of total protein, albumin and globulins in serum of rats (but not rabbits) in the 300 ppm group were lower than for controls. Gross lesions in rats and rabbits exposed to 300 ppm EGME included decreased size of thymus in both sexes, decreased abdominal fat, and small flaccid testes in males. In addition there was decreased lymphoid tissue in some rabbits, as well as a slight-to-moderate decrease in size of testes in 4 of 5 rabbits in the 100 ppm group and in 2 of 5 rabbits exposed to 30 ppm. Treatment-related microscopic lesions included degenerative changes in germinal epithelium of testes in all male rats and rabbits in the 300 ppm group, as well as in 3 of 5 rabbits in the 100 ppm group and 1 of 5 male rabbits in the 30 ppm group. The only effects attributed to exposure to 30 ppm EGME in this study were slight microscopic changes in testes of 1 of 5 male rabbits.