An analytical procedure was developed that enables routine analysis of four estrogenic hormones in concentrations below 1 ng/l in surface water and waste water. The recovery was 88-98% with a limit of detection of 0.1-2.4 ng/l depending on the compound and the matrix measured. This method was used to determine the occurrence of 17β-estradiol, 17α-estradiol, estrone and 17α-ethinylestradiol in the aquatic environment in The Netherlands. The data show that estrogenic hormones can be detected at low concentrations (up to 6 ng/l) at some locations in surface water. In selected effluents of waste water treatment plants estrone and 17β-estradiol were detected in concentrations in the ng/l range. Concentrations of 17α-estradiol and the contraceptive 17α-ethinylestradiol were in most of these samples below the limit of detection. Hormone glucuronides were not detected in most surface water and effluents. Copyright (C) 1999 Elsevier Science B.V. All rights reserved.