Ninety-two women with common epithelial tumors of the ovary and 105 comparison women admitted for various orthopedic conditions were interviewed regarding demographic, socio-economic and biomedical characteristics, including their use of coffee and tobacco. There was no association between tobacco smoking and ovarian cancer. However a statistically significant trend association was noted between coffee drinking and ovarian cancer (p approximately 0.03). The association could not be explained in terms of any other variable included in the present study. The relative risk for women drinking two or more cups of coffee per day was 2.2 with 95% confidence limits 1.0-4.8. Several descriptive epidemiologic data are compatible with a causal association between coffee and ovarian cancer.