A method for the quantitative determination of perfluorooctanoic acid in plasma by gas chromatograph-electron capture detector is described. An HP-1 capillary column (30 m x 0.25 mm i.d. x 0.25 micron) was used. Perfluorodecanoic acid as the internal standard was added to plasma sample, which was then lyophilized. The acids were derivatized to their methyl esters and then extracted into hexane. The calibration curve was linear over a range from 20.00 micrograms/L to 4.00 x 10(3) micrograms/L with a correlation coefficient of 0.9946. The average recovery was 99.2% and the RSD was 0.95%. The detection limit was 6.0 micrograms/L. The level of perfluorooctanoic acid in plasma of related occupational workers was measured. The results showed that this method is accurate and reliable.