Concern over certain classes of organic contaminants has heightened because they have been shown to mimic estrogen, disrupting the endocrine system and affecting sexual and other estrogen related development in vertebrates at low concentrations. Vitellogenin (Vg), is a very sensitive indicator of xenoestrogenic pollutants in fish. Vg production is limited to females, when males are exposed to xenoestrogenic compounds Vg was produced, and testosterone was depressed (Folmar et al 1996). This research proposes to document a Vg cycle from sunfish caught in a polluted site compared to a 'clean' site. Livers from specimens archived in Tulane's museum of Natural History 20 years ago from the same sites will be compared to current findings. Vg analysis will be done by western blotting, and livers will be analyzed for Vg using immunohistochemical methods. The goals of this research are to assess present day and historical risks posed by contaminants and water quality changes, actually establishing a biotic monitoring program in a heavily industrialized area where humans use fish as a food source.