The clinical significance of vimentin intermediate filament (VIF) expression was studied in relation to other established prognostic parameters in primary breast cancer. Archival tumour samples embedded in paraffin were examined by immuno-histochemistry with monoclonal antibodies (MAbs) to VIF, p53 protein and cell proliferation marker MIB-I. The vimentin staining pattern was heterogeneous, but in vimentin-positive areas > 80% of the tumour cells were positive. There was no association between vimentin expression and tumour size or the number of axillary lymph nodes involved. Vimentin expression was significantly associated with high-grade tumours, absence of hormone receptors, increased p53 expression and high tumour proliferation fraction as estimated by MIB-I count. Despite these associations with several recognised features of tumour aggressiveness, vimentin expression was not associated with increase in risk of relapse or death from breast cancer.