This study was carried out to evaluate the occurrence of the fluoroquinolone antimicrobial agent ciprofloxacin (CIP)in the effluent of the Hospital of the Federal University of Santa Maria (HUSM). Measured environmental concentrations (MECs) of CIP in the hospital wastewater, both before (P1) and after (P2) cesspit/filter system treatment (CFTS), were determined by means of solid phase extraction and reversed-phase liquid chromatography with fluorescence detection (LC-FLD) and reversed-phase liquid chromatography with mass spectrometric detection (LC-MS/MS). The MECs (n = 7 daily composed samples) were 19 to 155 μg L-1 (average: 54 ± 21 μg L-1) and 32 to 99 μg L-1 (average: 65 ± 45 μg L-1) in P1 and P2, respectively. No relevant removal was observed from P1 to P2. In a worst case scenario, the final effluent was regarded as MECs of surface water. These MECs were generally 5 to 20,000-fold higher than what was previously known. If the present data is drawn on to form a model of the situation in developing countries, the picture provides a first rough indication that the environmental risk associated with the use and emission of pharmaceuticals into the environment in developing countries might be higher than in developed countries. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.