We developed DNA microarrays for evaluation of estrogen activity by using human genes which are responsive to estrogen, a female hormone. A total of 203 genes were spotted on a microarray and mRNA from cells of various tissue origins was used for monitoring changes in gene expression before and after treatment of the cells with estrogen or chemicals suspected to have estrogen activity. We will apply this technology for evaluation of endocrine disruptors, screening supplements and medicines, therapeutics and others.