Human serum aspartate amino- transferase(AST) activity was measured voltammetrically at a gold micro electrode. 2,6- dichloroindophenol(DClP) was used as the redox mediator and electroactive species. Sensitive measurements free from spectrophotometric interferences can be made by a differential pulse voltammetric detection technique. The instrumentation is simple and inexpensive. The method yields reproducible results that were in excellent agreement with those obtained using the standard spectrophotometric method for determining serum AST activity in the clinical laboratory.