A method for the routine determination of platelet-produced thromboxane B2 (TXB2) from human serum is presented. To induce the secretion of thromboxane A2 from the platelets, blood is kept at 37 degrees C for 30 min before serum is separated. Serum is prepurified through small reversed-phase columns and TXB2 is analysed by reversed-phase high-performance liquid chromatography. A column-switching technique is used to remove the interfering compounds present in serum. The detection limit with standard solution is 30 ng per injection. The method was applied to the measurement of platelet-produced TXB2 serum from 1040 men. The mean TXB2 was 247 +/- 134 ng/ml in the serum of men who had not used prostaglandin inhibitors, and 208 +/- 123 ng/ml in the serum of men who had used a prostaglandin inhibitor during a two-week period before blood sampling.