Piper longum Linn. and Piper nigrum Linn. are used as spices and medicines. Quantitative determination of piperine was undertaken to provide an easy and simple analytical method, which can be used as a routine quality control method. RP-HPLC was performed using methanol and water as mobile phase. The detection and quantification was performed at a wavelength of 345nm. Linearity of detector response for piperine was between the concentrations 0.005% to 0.1%. The correlation coefficient obtained for the linearity was 0.998. The assay value of piperine for fruit and root of P. longum was found to be 0.879% and 0.31%. The assay value of piperine for fruit of P. nigrum was 4.5%. The recovery value of standard piperine was 99.4%. Low value of standard deviation and coefficient of variation are indicative of high precision of the method.