We report a case of bilateral breast carcinoma in a patient with a strong family history, including 4 cases of breast carcinoma, 1 case of prostate carcinoma (father), 1 case of hepatocellular carcinoma (mother), 2 cases of gastric carcinoma, 1 case of lung carcinoma, and 1 case of lingual carcinoma, in second degree relatives, together with analysis of germ line p53 mutations. The patient was a 51-year-old female who had undergone mastectomy 9 years previously for an invasive ductal carcinoma of the right breast. Lymph nodes were free of metastases and the tumor had negative estrogen receptor (ER) status. Bone and lung metastases developed 18 months after surgery, and had been well controlled with chemoendocrine therapy. She subsequently underwent a modified radical mastectomy for carcinoma in the contralateral breast. This was an invasive lobular carcinoma with negative lymph node metastasis, negative p53 immunoreaction, negative c-erbB-2 protein and positive ER status. In this breast-prostate carcinoma-type cancer family there was a high incidence of breast carcinoma; the father, who had prostate carcinoma, was possibly a carrier of a breast carcinoma susceptible gene. We have however detected to p53 germ line mutations in the lymphocytes DNA of the patient and her niece. The accumulation of cancers in this family line remains to be elucidated further using other genetic markers.