In 65 patients with primary invasive ductal breast carcinoma the relation between classic prognosticators describing the extent of disease (lymph node metastases and tumour size) and newer promising morphometric and DNA flow cytometric prognostic factors was studied. There was no relation between DNA ploidy, lymph node state, and tumour size. Tumours with a mitotic activity index of more than 10 were predominantly DNA aneuploid (61%) compared with those with a mitotic activity index of less than 10 which showed a DNA aneuploid pattern in 27%. The strongest prognosticator, the morphometric prognostic index (a multivariate combination of mitotic activity index, tumour size, and lymph node state) correlated positively with the DNA index in 63% of the cases (p = 0.038). Thus there was a discrepancy between the morphometric and DNA flow cytometric prognostic variables in 37% of the cases. These results indicate that morphometric and flow cytometric analysis may provide additional information on the prognosis in primary breast cancer.