Pharmacokinetics of acebutolol have been studied in hypertensive aged patients (79.4 +/- 3.8 years) and in young healthy subjects (23.4 +/- 0.7 years) after intravenous (0.35 mg/kg bolus) and oral administration (400 mg). Acebutolol and diacetolol, the main metabolite, plasma levels were determined by high-pressure liquid chromatography. After intravenous administration, apparent volume of distribution (1.5 vs. 2.4 liter . kg-1, p less than 0.05) and total body clearance (6.2 vs. 8.8 ml . min-1 . kg-1, n.s.) of acebutolol are smaller in elderly than in young men. After oral administration, maximum plasma levels (28.03 vs. 9.68 micrograms . l-1 . kg-1) and area under the curve (163.1 vs. 57.5 micrograms . l-1 . h . kg-1) are significantly higher in aged patients than in young subjects (p less than 0.001). Acebutolol and diacetolol plasma half-lives increase in elderly patients (11.6 vs. 7.2 h and 14.8 vs. 12 h respectively). These results suggest a possible accumulation of acebutolol and diacetolol in elderly.