The electrochemical properties of aciclovir (Acy) were studied by square wave voltammetric method (SWV) over pH range 1.5-8.0 using a controlled growth mercury, drop electrode (CGMDE). In the acid medium the cathodic peak current was observed. Surface catalytic electrode mechanism based on the hydrogen evolution reaction was analyzed. The dependence of the peak current at about -1.3 V vs Ag/AgCI electrode on pH, buffer concentration, nature of the buffer, amplitude, frequency and scan rate was investigated. The best results were obtained in solution of nitric acid at pH 1.9. This electroanalytical procedure enabled to determine aciclovir in the concentration range 2 x 10(-7)-2 x 10(-6) mol L-1. Repeat-ability, precision and accuracy of the developed method were checked. The detection and quantification limits were found to be 7 x 10(-8) and 2 x 10(-7) mol L-1 respectively.