To assess the feasibility of an exercise-diet intervention in sedentary, overweight breast cancer patients, we conducted a pilot 8-week intervention. Recruitment letters and interest surveys were sent to 99 stage 1 or 2 breast cancer patients, ages 25-75 years, who were identified through two Seattle breast surgery practices and the University of Washington Breast Clinic. Ten patients were eligible and interested and were enrolled in the intervention, which consisted of thrice-weekly monitored aerobic exercise sessions and a low-fat (20% of calories from fat) diet. Nine patients completed the program; all adhered well to the intervention and data collection protocol. The patients, ages 40-74 years, lost, on average, 2.6 pounds of body weight, 3.4 cm in waist circumference, 4.6 cm in hip circumference, 2.3% body fat, 3.3 systolic blood pressure points, 0.67 diastolic blood pressure points, and 4.0 pulse beats/min, and they gained an average of 2.3% lean mass. Slight, nonsignificant decreases were observed in serum concentration of total and free estradiol, estrone sulfate, total testosterone, androstenedione, and dehydroepiandrosterone. These pilot data indicate that breast cancer patients are highly motivated to join and adhere to an intense exercise-diet intervention and can experience significant measurable changes in anthropometric and fat mass measures.