A sensitive and specific method for the quantitative determination of tiadenol in human plasma is described. After addition of the internal standard, both compounds were quantitatively extracted into chloroform and then derivatized with heptafluorobutyric anhydride (the structures of both derivatives were confirmed by electron impact mass spectrometry). Quantitation was achieved by capillary gas chromatography, using a (63) Ni-electron capture detector. Linearity was observed in the concentration range 5-100 ng ml(-1) and the minimum concentration of tiadenol detectable in plasma was 2.0 ng ml(-1). The method was successfully applied to plasma specimens collected from healthy human volunteers following a single oral administration of 800 mg of tiadenol.