Transdermal drug delivery has been applied to various agents in an effort to decrease the frequency of drug administration and increase the patients compliance. In our study, we demonstrated that transdermal application of a beta-blocker (20 mg mepindolol) in patients with essential hypertension led to effective blood pressure lowering effect within 1 week (160.1 +/- 6.1 mm Hg/95.8 +/- 8.3 mm Hg vs 136.8 +/- 7.2 mm Hg/84.3 +/- 5.0 mm Hg; P less than 0.05). A controlled study of transdermal versus oral beta-blocker administration in hypertensives is necessary before this new therapeutic system is introduced in antihypertensive treatment.