The paper reports a recent efforts to develop and validate an efficient and rapid analytical assay method by GC/ GCMS for a series of 2H-benzoxazinone based 3-aryl-3,4-dihydro-2H-benz[e]-1,3-oxazin-2-one. Such compounds possess potent pharmacological importance and are of the class of efavirenz, a non-nucleoside reverse transcriptase inhibitor (NNRTI). Chromatography was performed with a non-polar capillary column, Rtx-5 (length 30 meter, id 0.25mm and film thickness 0.25μm), carrier gas nitrogen/ helium used at flow rate 1.20 ml/minute with split/splitless injector and flame ionization detector. GC oven temperature was programmed from 80°C hold for 1.0 min. and then increase at rate 15°C/min to 160°C, held isothermal at 160°C for 1.0 minute, temperature again increased at rate 20°C/min.to 260°C, held isothermal at 260°Cfor 5 minute and increase to final temperature at rate 20°C/min. to 280 °C held isothermal at 280 °C for 5 minute. Injector and detector temperatures were optimized 260°C and 280 °C respectively. Each analysis required 20minutes for separation of a series of all seven analytes. The method was validated for linearity, accuracy, precision, specificity, system suitability, and robustness. The method proved to be accurate, precise, specific, rapid, and reproducible according to ICH standards. The method showed good recoveries (99.50 to 100.50 %) for all analytes, and the relative standard deviations of intra- and inter-day were <2.0%. LOD and LOQ were from 0.17 to 0.34μg mL-1 and 0.51 to 1.02μg mL-1 for all analytes. This method has shown to be convenient for routine analysis of3-aryl-3,4-dihydro-2H-benz[e]-1,3-oxazin-2-one.This method is novel since there has been no report about analysis of benz-1,3-oxazine-2-ones derivatives or its class at μg mL−1 levels using a simple GC method