A cohort study was conducted to estimate the risk of breast cancer recurrence among women diagnosed with ductal carcinoma in situ (DCIS) and to identify tumor or patient characteristics that influence that risk. A population-based cancer registry was used to identify a cohort of 709 female residents of western Washington who were diagnosed with DCIS between January 1980 and June 1992 and were treated with breast-conserving surgery. Information about breast cancer recurrences, treatment, and several patient characteristics and exposures was obtained from postal questionnaires. Recurrences were confirmed using information from the cancer registry or hospital pathology reports. Approximately 15% of women experienced a recurrence within the first 5 years after diagnosis [95% confidence interval (CI), 12-18%]; 31% had a recurrence within 10 years (95% CI, 24-38%). There was a suggestion that risk was slightly elevated for women with larger tumors (> or =1.5 cm) and tumors of comedo subtype. Relative risks (RRs) were elevated for women who were premenopausal at diagnosis of DCIS (RR = 2.3; 95% CI, 1.1-5.0). Women in the upper decile of body mass index were at twice the risk of a recurrence as those women in the lower four deciles (RR = 2.3; 95% CI, 1.1-4.8). There was also a suggestion that women who used menopausal hormones for at least 2 years after their diagnosis of DCIS were at increased risk of recurrence compared to nonusers of menopausal hormones (RR = 1.8; 95% CI, 0.7-5.0). Our results suggest that the risk of recurrence may be related to some tumor characteristics as well as the hormonal milieu of the patient at or after her diagnosis of DCIS. However, larger studies are needed to more clearly document predictors of disease recurrence after DCIS.