Greggi and Kerlikowske have worked out that a woman has a 1.4% chance of developing ovarian cancer during her life. When cancer of the ovary is found, 5 to 10% of these cases have a familial form of this pathology. Thus there are some hereditary forms of cancer of the ovary and Lynch has demonstrated that there are three types of hereditary associations with ovarian neoplastic pathology: specific familial cancer of the ovary, cancer of the ovary associated with endometrial cancer and with non-polypoidal cancer of the caecum and rectum, cancer of the ovary associated with cancer of the breast. The clinical material we are presenting here is of the first type of association and we are reporting the study of a family in which 6 members in two generations had cancer of the ovary and of whom one had cancer of the breast as well. Familial cancer of the ovary shows different characteristics coming on as it does earlier (ten years earlier) and with a shorter length of survival (1.8 as against 5 years). The risk of the next generation having ovarian neoplastic pathology is clear because there is a 50% chance in a patient who has a history of cancer of the ovary in at least two first degree relatives. For most daughters when this type of familial cancer is found it is justifiable to carry out prophylactic oophorectomy from the age of 35 year onwards. Particular supervision should be carried out for patients who are members of a family where 2 index cases have been found within 20-35 years.(ABSTRACT TRUNCATED AT 250 WORDS)