The anodic behavior and determination of Valacyclovir (VALA) on boron-doped diamond (BDD) electrode was investigated using cyclic, differential pulse and square wave voltammetric tecnique. The oxidation of VALA was irreversible and exhibited diffusion controlled process depending on pH. Differential pulse (DPV) and square wave voltammetric (SWV) methods were developed for its determination in pharmaceutical dosage forms and biological fluids according to the linear relation between the peak current and VALA concentration. The peak current is found to be linear over the range of concentration 8 x 10(-7) to 1 x 10(-4) M in phosphate buffer at pH 4.0 for differential pulse and 2 x 10(-6) to 1 x 10(-4) M in phosphate buffer at pH 6.0 for square wave voltammetric technique using boron-doped diamond electrode. The repeatability and reproducibility of the methods for all media (supporting electrolyte, serum and urine samples) were determined. Precision and accuracy were also cheched in all media. The standard addition method was used for the recovery studies. No electroactive interferences were found in biological fluids from the endogenous substances and additives present in pharmaceutical dosage form.