In a double blind study, planned as a 7 x 7 latin square, three oral doses of flutonidin (0.5, 1, 2 mg), of clonidine (0.0075, 0.150, 0.300 mg) and of a placebo were administered to 7 normal volunteers on 7 different treatment days, with an interval of 3 days. On each treatment day sitting blood pressure, heart rate and reaction time were measured, and sedation and dry mouth evaluated before the 1, 2, 3, 4, 6, and 8 h after administration. The placebo did not modify the basal value of any variable. Flutonidin and clonidine produced dose-related effects on blood pressure, heart rate, sedation and dry mouth, but did not influence reaction time. Analysis of the dose-response curves demonstrated that the effect of flutonidin was one-fifth to one-twelfth that of clonidine, depending on which variable was considered.