A new high-performance liquid chromatographic (HPLC) method with fluorescence detection is described for the direct determination of four serum 17-oxosteroid sulphates. Each serum sample was deproteinated with methanol, the methanol was evaporated and 17-oxosteroid sulphates in the residue were extracted with benzene as ion pairs in the presence of tetrapentylammonium ion. The ion pairs were labelled with dansylhydrazine and the hydrazones were separated by HPLC on a Capcell-Pak C8 (silicone polymer-coated silica gel modified with octyl groups) reversed-phase column using methanol-0.5% (w/v) sodium acetate-50% (v/v) acetic acid (57:42:1, v/v/v) as the mobile phase. The eluent was monitored with a fluorometric detector at an excitation wavelength of 330 nm and an emission wavelength of 540 nm.