The occurrence of antibiotics including chloramphenciol (CAP), oxytetracycline (OTC) and tetracycline (TC) was studied in municipal sewage, river water and sediment. Temporal and spatial variations of antibiotic concentrations in municipal sewage, river water and sediment were evaluated. In municipal sewage, CAP, OTC and TC concentrations were in the range of 5.8-47.4, 0.16-5.7 and 0.7-65.2 microg L(-1), respectively, and showed a temporal variation with high antibiotic concentrations appearing in the cold season. Untreated municipal sewage can seriously influence both river water and sediment. Generally, high antibiotic concentrations in river water appeared in winter owing to the low flow condition as well as the high antibiotic concentration in the sewage. However, high CAP and OTC concentrations in sediment were observed in summer most likely because runoff in high flow season can carry wastes from some origins (e.g. livestock farms in the countryside) into the river. The partitioning of antibiotics in river water and sediment suggests a lower sorption of TCs to the sediment compared to previous studies, which is believed to be caused by the high Ca2+ and Mg2+ concentrations, ionic strength and pH of the river water in the carbonate area.