Objective: Cellular adhesion molecules ICAM-1 and VCAM-1 have been implicated in tumor progression and metastasis. As the sequential interaction of neoplastic cells with the endothelium of tumor neovascularisation is believed to be essential for tumor meta­stasizing processes, we analysed the concentration of ICAM-1 and VCAM-1 in the cytosol of patients with human breast cancers and their corresponding sera. We compared the obtained values with established prognostic parameters for breast cancer. Benign breast tissues were also analyzed. Patients and methods: Levels of ICAM-1 and VCAM-1 of 62 patients with invasive breast cancer and 17 patients with benign breast tissue were measured using commercially available sandwich enzyme-linked immunoassays with monoclonal antibodies. To establish a reference and control group, levels of ICAM-1 and VCAM-1 were measured in the sera of 66 women without breast tumors. Results: The mean cytosol concentration of ICAM-1 and VCAM-1 was significantly higher in the breast cancer specimens than in the tissue of patients with benign breast diseases. This could be found not only in the tumor cytosol but also in the correspon­ding sera of the patients. No correlations between the ICAM-1 and VCAM-1 expressions and established prognostic parameters could be observed. Conclusions: Our findings suggest that malignant breast cancer cells could induce neovascularisation with subsequent high expressions of ICAM-1 and VCAM-1. These upregulations of adhesion molecules might contribute to changes in invasive phe­notypes by promoting endothelial cell adhesion and angiogenesis, as well as being responsible for the recognition of tumor cells by the human immune system. Prognostic relevance for the development of breast cancer could not be established.