A large number of estrogen-mimicking, anthropogenic chemicals capable of disrupting normal reproductive function have been identified. The ubiquitous distribution of these compounds, many as components of complex industrial or municipal waste, has spurred an effort to develop methods to screen for chemicals which disrupt normal endocrine regulation of reproduction. We have developed assays that both allow exposure of animals in vivo and measure the response at the level of gene activation. We have developed a probe for measuring the induction of vitellogenin mRNA by Northern Blot in livers of sheepshead minnows treated with 17-β-estradiol. We have also developed a strategy for using Differential Display Polymerase Chain Reaction for determining gene induction profiles following exposure to estradiol. These methods should be adaptable to a variety of structurally diverse estrogen mimics.