The reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed to quantify metformin hydrochloride (MfCl) in raw material and pharmaceutical formulations using C(18) analytical reverse-phase column. Diazepam was used as an internal standard. Mobile phase consisted of methanol-water (30:70 v/v), pumped at a flow rate of 0.5 ml/min at ambient temperature and the retention time was about 4.4 min with symmetrical peaks. (MfCl) was detected by ultraviolet absorbance at 233 nm with no interference of commonly used excipients. The method was linear over the concentration range 0.312-5 mug/mL (R2 = 0.9995). The limit of detection of metformin was 0.1 mug/mL and the limit of quantitation was 0.3 mug/mL. The results obtained showed a good agreement with the declared contents in case of pharmaceutical formulations. The proposed method is rapid, accurate, economical and selective and it may be used for the quantitative analysis of metformin in Neodipar tablets because of its sensitivity and reproducibility.