The age-specific mortality rate of ovarian cancer is increasing among women over 50 years of age, but remaining at a stable level among women under 50. This case-control study of ovarian cancer was undertaken to assess the environmental factors which may increase the mortality of the disease in the elderly. Fifty-six women with primary epithelial ovarian cancer whose ages were 50 years old or over were compared with two age-matched control groups. The results of the Mantel-Haenszel analysis were as follows. More cases were found to have never married than controls (P less than 0.05), a larger proportion of cases were nulliparous (P less than 0.05), a smaller proportion of cases had experienced an induced abortion (P less than 0.05) or had undergone permanent sterilization by tubal ligation (P less than 0.05), the occurrence of breast or uterine cancer was more common in the mother or sisters of cases (P less than 0.01), a larger percentage of cases used to eat meat daily (P less than 0.01) or used to eat fish daily (P less than 0.05), and a larger proportion of cases weighed under 40 kg (P less than 0.05). Daily meat consumption was significantly associated with the occurrence of ovarian cancer even after adjusting for reproductive and other risk factors by conditional logistic regression analysis. The attributable risk for ovarian cancer in the elderly was 19.2% for daily meat consumption. The recent change in dietary habits might in part explain the rise of the mortality rate among the Japanese elderly.