The proposed HPLC method was found to be simple specific precise accurate rapid and economical for simultaneous estimation of Diphenhydramine and Naproxen in tablet dosage form The developed method was validated in terms of accuracy precision linearity robustness and ruggedness and results will be validated statistically according to ICH guidelines The Sample recoveries in all formulations were in good agreement with their respective label claims. Mobile phase was Ortho phosphoric acid buffer and Methanol in the ratio of 65:35 were set.Kromosil C18 coloumn was selected with dimensions  250×4.6mm, 5µ and with a flow rate 1.0 ml/min and temperature was ambient, eluent was scanned with PDA detector  and it showed maximum absorbance at 254 nm. As the methanol content was increased Diphenhydramine and Naproxen got eluted with good peak symmetric properties. The retention times for Diphenhydramine and Naproxen was found to be 2.589 min and 3.711 min respectively. System suitability parameters were studied by injecting the standard five times and results were well under the acceptance criteria. Linearity study was carried out between 50% to 150 % levels, R2 value was found to be as 0.999.

KEYWORDS : Diphenhydramine, Naproxen, RP-HPLC, detector and Linearity.