A sensitive method for detecting 17 beta-estradiol (E2) and estriol (E3) in river water has been developed, based on the time-resolved fluoroimmunoassay by using a fluorescent europium chelate label, 4,4'-bis(1",1",1",2",2",3",3"-heptafluoro-4",6"-hexanedion-6"-yl)- chlorosulfo-o-terphenyl (BHHCT)-Eu3+. In the E2 assay, microtiter plates were coated with the E2-bovine serum albumin (BSA) conjugate. The anti-17 beta-estradiol antibody, the biotinylated goat anti-rabbit IgG antibody and the BHHCT-Eu3+ labeled streptavidin (SA)-BSA conjugate were used. In the E3 assay, the goat anti-rabbit IgG antibody was coated on a microtiter plate. The anti-estriol antibody and the BHHCT-Eu3+ labeled E3-BSA conjugate were used. The detection limits for E2 and E3 were 2.3 pg/ml and 4.3 pg/ml, respectively, and the analytical recoveries were 95-120%. Quantitative measurement of estrogens in river water was carried out for Kanda River (Tokyo, Japan) by using the method. The E2 and E3 levels were 32 pg/ml and 5.5 pg/ml, respectively. The detection limits of the present method are in the same orders of magnitude as those of ELISA for E2, and are 1-2 orders of magnitude better for E3.