This paper describes validation of the selective, precise and accurate isocratic HPLC method for the assay of Gabapentin as bulk and pharmaceutical dosage forms. The mobile phase composition was ammonium dihydrogen orthophosphate buffer and methanol in 60:40(v/v) proportions Column used was strong cation exchange column bonded with phenyl sulphonic acid. Quantitation was achieved by UV detection at 200 nm. A linear response (r² ≥ 0.999) was observed in the range of 2.5 mg/mL -7.5 mg/mL. The method shows good recoveries (Average 101.2%) and the relative standard deviation intra and inter-day were found to be less than 0.5 %. Validation parameters were also determined. The method can be used for quality control assay of Gabapentin as bulk and in fnished dosage form and for the stability studies as the method separates Gabapentin from its degradation products and excipients.