An episode of community and occupational exposure to trichloroethylene (79016) (TCE) was described. In July 1979, 1900 gallons of TCE were accidentally released from a pipe manufacturing facility in Montgomery County, Pennsylvania. Ground water monitoring by the Pennsylvania Department of Environmental Resources showed TCE concentrations as high as 183000 parts per billion (ppb) within 1 kilometer of the facility. The Environmental Protection Agency recommended standard for TCE in drinking water is 5ppb. Concentrations decreased with distance from the facility. Peak concentrations were noted in August and levels gradually decreased over the next 6 months to below 10000ppb; however, concentrations of 5000 to 10000ppb persisted to 1985. Further study showed that TCE contamination of ground water in the county was widespread, suggesting a pattern of multiple releases. To evaluate community exposure, urine samples were collected from 13 Montgomery County residents and analyzed for TCE metabolites. Metabolites were found in two residents, at levels of 615 and 2.5 micrograms per liter (microg/l). To evaluate occupational exposure, breathing zone samples were collected in February and May 1980, before and after implementation of recommended improvements in ventilation and work practices. Urine samples from nine exposed workers and nine comparisons were analyzed for TCE metabolites. In February 1980, time weighted average (TWA) TCE exposures at the liquid vapor degreaser ranged from 117 to 357mg/m3, exceeding the NIOSH recommended standard of 135mg/m3. Excessive short term exposures were also noted. Metabolite levels increased over shift from 298 to 480microg/l. Seven exposed workers reported symptoms of drowsiness, dizziness, or confusion. In May, TWA exposures had been reduced to 84microg/l. Pre and postshift urinary TCE metabolite levels were greatly reduced. Fewer symptoms were reported. The authors conclude that community and occupational exposures to toxic chemicals may have a common origin.