Subchronic toxicity was evaluated in groups of 10 male CD rats and 10 male Syrian hamsters exposed by inhalation to 0, 101, 500, 991, or 2489 ppm tetrafluoroethylene (referred to as TFE, 99.3% minimum purity) 6 hrs/day, 5 days/week for 2 weeks. No clinical signs of toxicity resulting from TFE exposures were observed in rats and hamsters during the treatment period. After termination of exposure, rats exhibited a statistically significant decrease in serum albumin and albumin/globulin ratios at all exposure levels, although the effect was not dose related. Urinary fluoride in rats was elevated in a dose dependent manner at all levels, but differences were only significant in the 500,991 and 2489 ppm exposure groups. Other differences noted in rats included significant and dose dependent decreases in serum glutamic-pyruvic transaminase activity and urea nitrogen levels at the 500, 991 and 2489 ppm dose levels. Additionally, rats showed a significant depression in serum alkaline phosphatase activity in the 2489 ppm group. After 14 days of recovery all effects had disappeared in rats, except elevation of urinary fluoride. After termination of exposure, hamsters exhibited a significant increase in urinary fluoride excretion in the 991 and 2489 ppm groups. Serum albumin depression was significant in the 101 ppm exposure group. After the 14 day recovery period serum albumin depression was significant in the 500,991, and 2489 ppm exposure groups; urinary fluoride was at normal levels. Following 10 exposures, 5 of 5 rats exposed at the 2489 ppm level exhibited compound related kidney histopathology which disappeared after 14 days of recovery. No histopathological effects were observed in hamsters after 10 exposures, however, following the 14 day recovery period a significant increase in testicular atrophy was observed in the 2489 exposure group. Rats showed significant elevation of absolute and relative weights of liver and kidneys following the 10th exposure in the 991 and 2489 ppm exposure groups. These effects were not present after the 14 day recovery period. There were no significant differences in absolute or relative organ weights in hamsters exposed to any level of TFE.