An accurate and reproducible reverse phase high performance liquid chromatographic method has been developed for the estimation of olanzapine in its pure form as well as in its tablet dosage forms. The chromatography was carried out on a Kromasil C-18 column using a mixture of acetonitrile and phosphate buffer (30 : 70 v/v) as the mobile phase at a flow rate of 1.5 mL/min. The detection was done at 258 nm. The retention time obtained for the drug was 1.850 min. The method produced linear responses in the concentration range of 10 to 50 μg /mL of olanzapine. The method was found to be reproducible for analysis of the drug in tablets.