UCN-01, 7-hydroxystaurosporine, is an antagonist of protein kinase C, as well as causing cell cycle arrest. We developed and validated an HPLC assay method for the quantitation of UCN-01. Plasma and saliva standard curves were prepared at concentrations ranging from 0.2 to 20.0 mg/mL and 4.0 to 200.0 ng/mL, respectively. The sample preparation consisted of acetonitrile precipitation. Separation was accomplished on a phenyl column and a C-18 precolumn insert utilizing a gradient-profile consisting of ammonium acetate and acetonitrile. UV detection was set at 295 nm for UCN-01 and 323 nm for umbelliferone, the internal standard. For fluorescence detection, excitation occurred at 290 nm, while emission was at 400 nm. The retention times were around 4 min for umbelliferone and 9.1 for UCN-01. Inter-and intra-assay errors of accuracy were less than 7.0% and 10.7%, respectively, for the plasma standard curve and less than 7.1% and 6.7%, respectively, for the saliva standard curve. The recoveries of UCN-01 and umbelliferone from saliva were 81.4 AE 0.9% and 106.3 AE 10.2%, respectively. The recovery of UCN-01 from plasma was 97.9 AE 7.1% and for umbelliferone was 103.3 AE 2.3%. This method is suitable for quantifying UCN-01 in patient samples and further characterizing the clinical pharmacology of this compound. Published in 2000 by John Wiley & Sons, Ltd.