Pharmaceuticals are continually introduced into the environment as a result of industrial and domestic use. In recent years they have emerged as environmental pollutants. An analytical method has been developed allowing for simultaneous detection and identification of 20 pharmaceutical compounds from various therapeutic classes using solid phase extraction (SPE) followed by liquid chromatography-electrospray ionisation mass spectrometry (LC-MS/MS). The limits of detection and limits of quantitation for the method were in the ng/L-microg/L range. The method was applied to influent and effluent samples from three wastewater treatment plants (WWTPs). Fifteen compounds were identified in the sample matrix with salicylic acid and ibuprofen being the most abundant at 9.17 and 3.20 microg/L respectively.