A method for the simultaneous determination of losartan potassium and hydrochlorothiazide in tablets is described. The procedure, based on the use of reversed-phase high-performance liquid chromatography, is linear in the concentration lange 3.0-7.0 mu g ml(-1) for losartan and 0.5-2.0 mu g ml(-1) for hydrochlorothiazide, is simple and rapid and allows accurate and precise results. The limit of detection was 0.08 mu g ml(-1) for losartan and 0.05 mu g ml(-1) for hydrochlorothiazide. (C) 2000 Elsevier Science B.V. All rights reserved.