We developed a sensitive method based on solid-phase extraction and high-performance liquid chromatography coupled to mass spectrometry using an electrospray interface for the determination of four tetracyclines and two quinolones in water. The method was applied to river, well and sewage-treatment-plant waters. For the solid-phase extraction of 1000 ml river water samples, recoveries were between 88 and 112% and limits of detection were as low as 4 and 6 ng l(-1). Recoveries were higher than 64% for 1000 ml well water samples for the majority of the compounds. For the influent and effluent of the sewage-treatment-plant sample volumes of 100 and 250 ml were extracted, respectively. The method developed allowed ciprofloxacin to be determined in samples from the influent and effluent of the sewage-treatment-plant at 0.58 and 0.60 microg l(-1), respectively.