Aim of this study was to provide an up-to-date assessment of the antibiotics contaminating the aqueous environment in Italy, for a better understanding of risks for the ecosystem and human health. Antibiotics were first listed in order of their theoretical environmental loads, then were measured in wastewater of some sewage treatment plants (STPs) and in rivers in Italy. Macrolides, particularly clarithromycin and spiramycin, and quinolones, particularly ciprofloxacin and L-floxacin/ofloxacin, were the most abundant antibiotics in untreated wastewater. Several of them were not removed in STPs and still remained in the treated wastewater, and a total estimate of 7-14 tons of active principles were discharged annually into the aqueous environment in Italy through this route. Results of the analysis of rivers in northern Italy agreed with these figures, with an average load of 5 kg/day, or about 1.8 tons/year, of antibiotics flowing in the River Po, at sampling sites covering a basin comprising about one-fifth of the Italian population. In conclusion, antibiotics, particularly macrolides and quinolones, are widespread environmental contaminants, and urban STPs are confirmed a major source of the contamination. (C) 2010 Elsevier BM. All rights reserved.