Olmesartan Medoxomil (OLME) belongs to a group of angiotensin II receptor blockers used as an antihypertensive agent and is currently being used for prevention of Hypertension. This paper describes the Validation and development of stability indicating RP-HPLC method for the determination of OLME in the presence of its degradation products generated from forced degradation study and characterization of degradation product (impurity). The assay involved gradient elution of OLME on An LC GC BDS C18 column (250 × 4.5mm, 5-μm particle size) was employed for loading the sample. The mobile phase A consists of 7 ml Triethylamine in 1000 ml water (pH adjusted to 3.0 with orthophosphoric acid) and B contains acetonitrile. Quantification was achieved with photodiode array detection at 257 nm. The chromatographic separation was obtained with a retention time of 6.72 min, and the method was linear in the range 50-150 µg/ml. The method was validated according to the ICH guidelines with respect to linearity, precision, accuracy, limit of detection (LOD), limit of quantification (LOQ), specificity and robustness. Impurity found in stressed and stability studies of Olmesartan Medoxomil in both drug substance and drug product are described. This degradation product is identified as 1-(biphenyl-4-ylmethyl)-1H-imidazole-5-carboxylic acid. An Alkaline degradation pathway of Olmesartan medoxomil, for the formation of this degradation product, has been proposed and degradation product was characterized.