A cohort of 36 cases of advanced breast carcinoma were included in the study. DNA ploidy, histological grade, and immunoreactivity for carcino-embryonic antigen (CEA), carcino-embryonic antigen with normal cross-reacting antigen (CEA/NCA), and to NCRC-11 were assessed in primary breast carcinomas and metastases from the ovary and axillary lymph nodes. Changes in these variables between primary tumours and their metastases were found in 44 per cent of cases for DNA ploidy, 44 per cent of cases for histological grade, 17 per cent of cases for immunoreactivity to NCRC-11, 28 per cent of cases for CEA, and 56 per cent of cases for CEA/NCA immunoreactivity, respectively. Alteration of one factor appeared to be independent of changes in other factors. The development of clones with metastatic potential does not appear to be related to consistent changes in any one of the factors examined and suggests that none of these factors would be of prognostic value in advanced breast carcinoma.