Twelve volunteer students were experimentally exposed to 0, 27, 81 or 201 ppm trichloroethylene for 4 hours, and suffered from irritation to mucous membrane of eyes and throat at over 27 ppm trichloroethylene. No headache or physiological responses were reported at 27 ppm; headache occurred at levels over 81 ppm. Accumulated urinary excretion of total trichloro-compounds, trichloroacetic acid and trichloroethanol for 6 days after trichloroethylene exposure increased linearly with environmental trichloroethylene concentration in volunteers experimentally exposed to 0–315 ppm trichloroethylene.