The combination of pseudoephedrine and cetirizine is widely used in the treatment of allergic rhinitis. A rapid, selective and stability indicating high performance thin layer chromatographic method was developed and validated for their simultaneous estimation in pharmaceutical dosage forms. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of ethyl acetate-methanol-ammonia (7:1.5:1, v/v/v). This system was found to give compact spots for both pseudoephedrine (Rf value of 0.69 ± 0.01) and cetirizine (Rf value of 0.38 ± 0.01). Also the degraded products were well separated from the pure drugs. Spectrodensitometric scanning-integration was performed at a wavelength of 240 nm. The polynomial regression data for the calibration plots showed good linear relationship with r2 = 0.9947 in the concentration range of 10-26 μg for pseudeophedrine and 200-1200 ng for cetirizine with r2 = 0.9973. The method was validated for precision, accuracy, ruggedness and recovery. The minimum detectable amounts were found to be 2 μg and 500 pg for pseudoephedrine and cetirizine, respectively. The limits of quantitation were found to be 6 μg for pseudoephedrine and 800 pg for cetirizine. Both the drugs do not undergo degradation under acidic and basic conditions. The samples degraded with hydrogen peroxide showed additional peaks at Rf values of 0.75 and 0.28 for pseudoephedrine and cetirizine, respectively. This indicates that both the drugs are susceptible to oxidation. Statistical analysis proves that the method is reproducible and selective for the simultaneous estimation of pseudoephedrine and cetirizine. As the method could effectively separate the drugs from their degradation products, it can be employed as a stability indicating one. © 2001 Elsevier Science B.V.