Water samples from four Taiwanese wastewater treatment plants (WWTPs) employing secondary treatment processes were evaluated for a sweep of pharmaceuticals, and analysis of the mass loads and removal efficiencies of the compounds identified were conducted. Fifty-seven compounds were detected, including significant amounts of non-steroidal anti-inflammatory drugs (NSAIDs), psychostimulants (caffeine), antibiotics, and beta-blockers, as well as trace levels of estrogens, vasodilators, psychiatric drugs, and lipid-regulators. Total loads ranged from 10 to 13 and 1.2 to 3.3 g/(d 1000) inhabitants for influents and effluents, respectively. NSAIDs were the main constituent (61-69%) in the water entering three WWTPs. Removal efficiencies varied among WWTPs; high removal rates (72-100%) were generally achieved for NSAIDs, estrogens, and caffeine, but some antibiotics groups (macrolides, penicillin, and imidazole) were not removed at all in many cases. This study also identified 17 mostly detected and persistent pharmaceuticals, of which caffeine, cephalexin, atenolol, and ibuprofen had the highest influent concentrations (up to 17,500, 4367, 2883, and 17,933 ng/L). These medications are used worldwide in significant amounts, and as shown here, the residuals which escape WWTP processing emerge as the primary pollutants for downstream receiving water bodies. (C) 2009 Elsevier B.V. All rights reserved.