There is provided a highly specific and highly sensitive assay method for platelet-activating factor (PAF). The invention may be employed to measure PAF levels in biological samples for elucidating the role of PAF in various pathological conditions. In addition, it is expected to facilitate diagnosis of various diseases associated with PAF fluctuation, and also contributing to evaluation of therapeutic effects on such diseases. The invention is a method whereby PAF is selectively extracted and purified from a biological sample, and then the PAF is measured by highly sensitive and specific gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry.
