A RP-HPLC method was developed for the estimation of Ondansetron Hydrochloride in Bulk drug using high performance liquid chromatography. Ondansetron was a serotonin 5-HT3 receptor antagonist used mainly as an antiemetic drug to treat nausea and vomiting after cancer chemotherapy. The separation was achieved by Promosil C-18 (250 mm x 4.6 mm x 10 µm) column because it allows higher separation and Acetonitrile: Methanol (50:50) as mobile phase with a flow rate of 1.2 ml/min. The detection was carried out at 216 nm. The retention time of drug was found 2.64 min. The developed method was validated. The proposed method shall prove equally effective to analyze Ondansetron Hydrochloride in the corresponding drug sample and may prove to be of great importance in pharmaceutical analysis. KEYWORDS: Ondansetron, Acetonitrile, Antiemetic, Methanol.