Patients with endometrial or ovarian cancer have an increased risk of breast or colon cancer and vice versa. To study the individual and age-related characteristics of patients with a combination of these malignancies, we reviewed the hospital records of fifty-three patients who had endometrial or ovarian cancer diagnosed at the Turku University Central Hospital in 1977-1991, and who had a preceding, concomitant or subsequent diagnosis of breast or colon cancer. Forty-nine patients had two and four patients had three primary cancers. Breast cancer patients presenting with subsequent ovarian carcinoma had a clearly lower mean age at first cancer diagnosis than the general population mean for breast cancer (50.0 years vs 61.1 years). The mean age of these patients at the time of diagnosis of ovarian cancer was not lower than the general population mean for ovarian cancer (62.0 years vs 61.1 years). A genetic predisposition to both breast and ovarian cancer has been reported previously. More attention should be paid to breast cancer patients' family histories with respect to ovarian cancer, especially if the patient is premenopausal. This might help to identify women at risk of getting ovarian cancer later in life.