The photodegradation of 17alpha-ethynylestradiol (EE2) in aqueous solutions induced by UV-light was preliminarily studied in this paper by means of fluorescence, UV and infrared spectra. The result suggested that EE2 in aqueous solutions underwent photodegradation under irradiation with UV disinfection lamp (lambda = 254 nm, 30 W), but the photodegradation was not observed under high pressure mercury lamp (lambda greater than or equal to 365 nm, 250 W). The photodegradation of 1.6-20.0 mg/l EE2 in aqueous solutions at a given initial pH value of 6.8 was pseudo-first order reaction. Increasing the initial concentration of EE2 lowered the photodegradation rate. The photodegradation rate of EE2 reached the lowest value at pH about 5.0, higher pH values of 6.0-8.0 benefited the photodegradation. Ferric ions can promote the photodegradation of EE2 in aqueous solutions at pH value of 2.0-5.0. (C) 2003 Elsevier Science B.V All rights reserved.