We have gathered epidemiological data and blood from a population-based sample of epithelial ovarian cancer patients in Northern California. Among these patients, 667 (94 percent) have provided permission to obtain samples of their paraffin-embedded ovarian tissue. For this pilot study, we request funds to collect these tissue samples and to analyze them for specific protein expression patterns, as they relate to particular characteristics of the patients and their tumors. Specifically, this pilot study aims to: 1) determine expression levels of 10 proteins considered to be potentially important in the pathogenesis of ovarian cancer; and 2) compare expression levels across subgroups defined by patient characteristics, histopathological characteristics of tumor, and combinations of patient and histopathological characteristics. Our long-term aims (to be accomplished under future funding) are to: i) study many additional proteins involved in the hormonal and cell-cycle pathways represented by the current sample of proteins; and ii) relate protein expression levels to ovarian cancer survival and to germline polymorphisms that are associated with ovarian cancer risk. Detection of protein expression variation across patient and tumor characteristics should help to develop and evaluate potential screening tools for early detection and new treatment strategies. Such detection also may advance our understanding of the pathogenesis of ovarian cancer.