Abstract: Roxithromycin in environmental water was separated and enriched by solvent floatation, and determined by UV spectrophotometry. Floatation was carried out in a K2HPO4 solution of pH 9.0 with isopropanol as floatation solvent and by passing N2-gas through the solution at the rate of 15 mL·min-1 for 30 min. Linear relationship between values of absorbance and mass concentration of roxithromycin were obtained in the range of 8.2-40.2 mg·L-1, with detection limit (3S/N) of 0.26 mg·L-1. In testing for recovery by addition of standard roxithromycin solution at 3 concentration levels to samples of river and lake water, values of average recovery more than 90% were obtained.