Van Lake is the third largest closed lake in the world and the biggest lake in Turkey. An ELISA method has developed with the aim of determining the pollution caused by estrogens and estrogen-like chemicals that have come to the lake Van in recent years. First, the vitellogenin in estrogen-treated male fish plasma was purified by ion exchange chromatography, injected into rats, and the obtained polyclonal antibodies were tested for specificity by Western blot and immunohistochemical methods. Immunohistochemical labeling of the vitellogenin-synthesized liver resulted in the intense marking of the liver of the animals injected with estrogen, while no markings were observed in the control group. The limit of detection of the developed enzyme-linked immunosorbent assay was 4.6 mu g L-1, and the working range was 7.8 to 2000 mu g L-1. Intra- and inter-assay variations were 13.0 % and 13.3%. The highest level of vitellogenin in male fishes measured was 23.56 mu g mL(-1).