response for concentrations in the range of 1-200 ìg/mL using acetonitrile: formic Acid (90: 10); pH-3.0 as the mobile phase with detection at 274 nm and a flow rate of 1 ml/min and retention time 2.9 min. The method was statistically validated for accuracy, precision, linearity, rugge dness, robustness, forced degradation, solution stability and selectivity. Quantitative and recovery studies of the dosage form were also carried out and analyzed; the % RSD fromrecovery studies was found to be less than 1. Due to simplicity, rapidity and accuracy of the method, we believe that the method will be useful for routine qualitycontrol analysis. The acid degradation product as well as pathway was characterized by LC-MS/MS.RESULT AND DISCUSSIONA sensitive, selective, precise and accurate high performance liquid chromatographicmethod of analysis of doxofylline in both as bulk drug and in formulation was developed and validated. The mobile phase consisted of acetonitril: 0.05M formic Acid (90: 10v/v); pH-3.0. The detection wavelength was 274nm. This system was found to give the sharp peak for Doxofylline (RT-2.9). The method was validated as per ICH guideline. Stability indicating assay method in which alkali stress condition was used for quantitative estimation of doxofylline in tablet formulation and identification of alkali degradation product The separation of drug from its degradation product were optimized by varying the ratio &/or nature of organic modifier. Finally method was developed using samemobile phase composed of acetonitrile: formic Acid (90: 10); pH-3.0, in that both drug and degradation product showing good elution RT-2.9 (Doxofylline) and RT-5.1 (Alkalidegradation product) and m/e-262. The acid degradation product and pure drug were identified by LC-MS/MS in order to establish acid degradation pathway(fig.-04, 05and06).