The purpose of this project is to define through analytic studies the relationship of a number of distinct exposures to various cancer outcomes. Relationships have been defined through both retrospective as well as prospective approaches, with many of the studies utilizing laboratory probes to define exposures better. In several studies, the relationship of type-specific human papillomaviruses (HPV) to risk of cervical neoplasia was pursued using hybridization probes. These studies further clarified the relationship of risk to parity, screening behavior, smoking, oral contraceptive use, and female and male sexual behavior. The role of exogenous hormones was also studied in relation to cancers of the endometrium and breast, showing that the effects of oral contraceptives vary by the stage of breast cancer diagnosis and that combined estrogen/progestin therapy has different relationships with breast and endometrial cancers. Studies are currently ongoing to further investigate the role of exogenous hormones and other suspect risk factors for these two common female cancers. Furthermore, this project attempted to assess risk factors for several relatively unstudied cancer sites, including vulvar, vaginal and penile cancers, as well as hydatidiform mole. Also included were attempts to clarify relationships of drinking water contaminants to a variety of cancers, pesticide exposures to risk of leukemia and non-hodgkin's lymphoma, and therapy for rheumatoid arthritis to risk of subsequent hematopoietic cancers.