Abstract This paper describes the validation of an isocratic HPLC method for the assay of Efavirenz . Thiswork is concerned with application of simple, precise, accurate and reproducible reverse phase high performanceliquid chromatographic (RP-HPLC) method for simultaneous estimation of Efavirenz. The method employ aZodiac C18 column with Methanol and acetonitrile 80:20 (v/v) as the mobile phase and ultraviolet (UV) detectionat 280 nm. A linear response (r>0.998) was observed over the concentration range of 15-45 μg/ml. The resultsshowed good recoveries, ranging from 98.77 to 101.45% and the relative standard deviation (R.S.D.) intra-dayand inter-day were ≤ 0.80%.. As the method could effectively separate the drug from its degradation products, itcan be used in stability studies for drug substance. [avf_view name="Article Addons" view-id="66d98451c48e3"]