A sensitive, precise, and accurate method for rapidly analyzing body fluids for pentachlorophenol has been developed. The method includes acidification and extraction of the fluid with hexane. The extract is reacted with acetic anhydride, washed with buffer, and injected into a gas chromatograph fitted with an electron capture detector. Quantitation of the pentachlorophenol is based on the ratio of the peak height of pentachlorophenyl acetate to an internal standard, tribromophenyl acetate. The lower detection limit in urine or serum is 1-2 parts per billion. The method was applied to workers in pentachlorophenol formulating plants and to residents of pentachlorophenol treated log houses. Hydrolysis increased the yield of determined urinary pentachlorophenol by a factor of approximately 1.8. Serum levels of pentachlorophenol were 2-3 time higher than the corresponding whole blood levels.