A simple, selective, linear, precise, and accurate RP-HPLC method was developed and validated for the simultaneous estimation of Rupatadine and Montelukast from bulk and formulations. Chromatographic separation was achieved isocratically on a [email protected] Lichrosphere ® C18 column (250×4.6 mm, 5 μ particle size) using a mobile phase, Methanol and Potassium Di Hydrogen Phosphate buffer and Acetonitrile (adjusted to pH 3.0 with 1% orthophosphoric acid) in the ratio of 50:30:20v/v/v. The flow rate was 1 ml/min and effluent was detected at 226 nm and 20μl of sample was injected. The retention time of Rupatadine and Montelukast were 2.48 min and 6.38 min. respectively. Linearity was observed in the concentration range of 5-30 μg/ml for both Rupatadine and Montelukast. Percent recoveries obtained for both the drugs were 99.53-100.16% and 97.63-98.95%, respectively. The percentage RSD for precision and accuracy of the method was found to be less than 2%. The method was validated according to the ICH guidelines with respect to specificity, linearity, accuracy, precision and robustness. The method developed can be used for the routine analysis of Rupatadine and Montelukast from their combined dosage form.