A simple and cost effective, fast and precise reverse phase high performance liquid chromatographic method is described for the determination of efavirenz in pure form and in pharmaceutical formulations. This method is based on using a Luna 5 μ C18 column, the size of coloum 5 micron, 250 x 4.60 mm from phenomenex. The mobile phase is acetonitrile: water (0.02 M sodium dihydrogen orthophosphaste). The ratio of mobile phase is 70 : 30 v/v. the flow rate is 1 mL/min, and effluent was monitored at 270 nm. The elution time was 4.5 min. The linearity range was 10-60 μg/mL for efavirenz.