The electrochemical response of bisoprolol fumarate (BF) and propranolol hydrochloride (PR) is significantly enhanced by immobilization of a Nafion film on the surface of the glassy carbon electrode. The positively charged drug molecules were accumulated in 0.1 mol L(-1) sulfuric acid solution at a potential of +0.6 V for 120 s, and then determined by square-wave anodic voltammetry. The enhancement mechanism and effect factors such as pH value, mass of Nafion, accumulation potential and pre-concentration time, were explored. The peak current is proportional to the concentration in the range from 5 x 10(-8) to 5 x 10(-7) mol L(-1) for BF and from 8 x 10(-8) to 6 x 10(-7) mol L(-1) for PR, with the sensitivities of 1.49 x 10(8) and 2.47 x 10(7) mu A mol(-1) L, respectively. The modified electrode was used to determine both beta-blockers in commercial tablets. The quantification of BF in urine samples with no prior extraction was carried out after selective accumulation at the electrode surface under stirring. Together with low cost and ease preparation, the modified electrode is a promising sensor in electroanalysis, not only for the detection of BF and PR, but also for other p-blocker drugs. (C) 2011 Elsevier B.V. All rights reserved.