A study of 200 patients with breast cancer carcinoma at different stages of the disease, was carried out for detecting in their bone marrow, mammary cells and their proliferative condition using a double labelling method with two types of monoclonal antibodies. The mammary cells were visualised with monoclonal antibodies raised against human breast epithelium and/or carcinoma. DNA synthetising cells (in S phase) were detected on the same slide, using a monoclonal antibody directed against an antigen associated with bromodeoxyuridine (BrdU) after cell incubation with BrdU. Mammary cells could be detected in the bone marrow of 13 out of 20 cases presenting macroscopically visible metastasis, 12 out of 20 patients at diagnosis of their disease, 90 out of 160 patients in apparent disease free condition. The labelling index was 6/13, 6/12 and 45/90 in those respective three groups of patients. The similarity of these three groups for both parameters suggests that the fate of breast carcinoma patients and their prognosis in three types (++, +-, --) is carried from the beginning of the disease. We have, with Eriguchi shown that the mammary (and other) cancer patients survival exponential curves do not express homogeneous populations but are in fact composed of three segments, the first with a rapid slope represents the acute type patients, at high risk of early relapse, the second, with a slow slope, represents the chronic type patients at risk of late relapse and the third, the slope of which is parallel to the general population life expectancy, represents the so called "cured patient".(ABSTRACT TRUNCATED AT 250 WORDS)