In an effort to determine if differences exist in the treatment and outcome of patients with suboptimally debulked stage IIIc and IV epithelial ovarian cancer between two tertiary-care cancer centers in Canada and the United States, we conducted a comparative study. The records of all patients who underwent treatment for epithelial ovarian cancer at two tertiary-care cancer centers in Canada and the United States between 1987 and 1989 were abstracted onto a common datasheet which was then entered into a computerized database for analysis. Only patients with suboptimally debulked stage IIIc disease (residual tumor diameter > 1 cm) or stage IV were included in the comparative study. There was a total of 129 evaluable patients (61 Canadian, 68 American). There were no statistically significant differences between the centers in mean age, performance status, histology, grade, or stage distribution. During the period of this study there was no statistically significant difference between the two institutions in the proportion of patients in whom optimal debulking was achieved (Canadian 19%, American 26%). The American patients were heavier than the Canadian patients (Quetelet index 27.3 vs 23.8, P < 0.006). Primary chemotherapy included a platin-containing regimen in 98 and 93% of Canadian and American patients, respectively. The average number of laparotomies each patient received during her course of illness was 1.7 and 2.5 at the Canadian and the American centers, respectively (P < 0.0001). Similarly, the American patients received a higher mean number of different chemotherapy regimens and total number of courses of chemotherapy during the course of their disease (3.0 and 12.6) than did the Canadian patients (2.4 and 8.8) (P < 0.01 and P < 0.001, respectively). The median survival was 21 months and 20 months in the Canadian and the American patients, respectively (no significant difference), and the 5-year survival was 10% for the Canadian and 11% for the American patients. Despite significant differences in the overall aggressiveness of treatment between the two centers, there was no difference in the survival of these patients. Until effective salvage agents or treatment strategies are realized, "more is not necessarily better."