A simple and highly sensitive method based on poly-1,5-diaminonapthalene (p-DAN) modified pyrolytic graphite sensor (MPGS) is delineated for the simultaneous determination of acetylsalicylic acid (ASA), paracetamol (PAR) and caffeine (CF) in nanomolar concentrations in human urine. The electrooxidalion of ASA, PAR and CF occurred in well defined peaks at pH 7.2. After optimization of analytical conditions exploiting this sensor, the peak currents for the three compounds were found to increase linearly with increase in their concentration in the range of 0.1-120 nM and detection limits of, 0.93 x 10(-10), 0.57 x 10(-10) and 0.64 x 10(-10) M were observed for ASA, PAR and CF respectively. The sensor was also successfully employed for the simultaneous determination of all the three compounds in human urine and pharmaceutical samples using square wave voltammetry (SWV). As a conducting polymer modified sensor has been used, several advantages, such as a very low detection limits, high sensitivity, long stability and excellent reproducibility were observed. The method is selective and all the three compounds can be determined effectively in human urine samples without any interference from common urine metabolites such as uric acid and ascorbic acid. (C) 2013 The Electrochemical Society. All rights reserved.