A simple and accurate gas chromatog. head space method was developed for the determination of 1, 3 Dibromo Propane in the Olopatadine Hydrochloride bulk drug. Chromatog. separation between 1, 3 Dibromo Propane, diluent and residual solvents used in Olopatadine Hydrochloride was achieved using a DB-624 (30 m x 0.53 mm x 3.0 μm) column using nitrogen as carrier gas. The resolution between the between 1, 3 Dibromo Propane and Benzyl alc. as diluent was found to be more than 5.0. The Limit of Detection (LOD) and limit of quantification (LOQ) of the 1, 3 Dibromo Propane was 1.46 and 4.37 μg mL-1, resp. The percentage recoveries of the 1, 3 Dibromo Propane ranged from 95.1% to 111.5 in the samples of Olopatadine Hydrochloride. The developed method was validated as per International Conference on Harmonization guidelines in terms of specificity, limit of detection, limit of quantification, precision, linearity, accuracy and ruggedness.