We investigated 24 families who satisfied a set of criteria for hereditary breast cancer. Five families had only breast cancer, four a combination of breast and ovarian cancer and the remaining 15 had also a variety of other cancers. The families include 86 patients, 78 of which had a malignant tumour and the rest had a benign lesion in the breast. The median age at diagnosis of the breast cancer was 47 years. Three of the 24 families were of a late onset variant. 58 of the 86 patients were symptomatic while 18 were identified during presymptomatic screening because of a positive family history. In 10 cases the reason for referral was not known. 56 of the symptomatic patients had a malignant breast lesion, 52% of which were with lymph node metastasis whereas 12 of the screening group had breast cancer with 2 patients showing lymph node involvement (P = 0.06). 22 of the symptomatic patients and none of the screening patients died of breast cancer after a median observation period of 6 and 7 years, respectively (P < 0.05).