BACKGROUND: The optimal treatment for patients with stage II ovarian cancer is controversial, although most experts recommend adjuvant chemotherapy. The purpose of this study was to assess the patterns of use of chemotherapy in women with stage II ovarian cancer, and to compare the survival of treated and untreated patients aged 65+ years in a population-based sample. METHODS: Using the Surveillance, Epidemiology, and End Results (SEER)-Medicare database of cancers diagnosed in approximately 14% of the U.S. population, we identified women who were diagnosed with stage II ovarian cancer between 1992 and 1996, survived >or=120 days beyond diagnosis, and were >or=65 years of age. Multivariate regression was used to compare those treated to those not treated with chemotherapy. Cox proportional hazards regression models were used to analyze patient survival. RESULTS: Of 236 women with stage II ovarian cancer, 160 (67.8%) received chemotherapy, and 118 (50%) received platinum-based regimens. Younger patients and those with higher-grade tumors were more likely to receive chemotherapy. The adjusted hazards ratio for mortality associated with any chemotherapy use was 0.67 (95% CI, 0.45-0.98), corresponding to an increase in median survival from 28 months to 35 months (P < 0.0001). CONCLUSIONS: This observational study found that most patients aged >or=65 years and diagnosed with stage II ovarian cancer between 1992 and 1996 were treated with chemotherapy. Grade and younger age were the most significant predictors of treatment, and treatment was associated with a 5-year mortality reduction of 33%. These findings are not definitive, but they may provide some guidance in the absence of randomized trials of adjuvant chemotherapy for older women with stage II ovarian cancer.