Malignant melanoma and primary breast cancer are tumours which have an association based on genetic and hormonal factors. It is not generally appreciated that there is an increased incidence of melanoma in patients with breast cancer and vice versa. We present two cases of patients who developed breast carcinoma following previous treatment for melanoma. We review previous reports of this association and examine the theoretical reasons why this should be so. Medical practitioners should be aware of this association in order to alter their index of suspicion appropriately.