Twenty-one high-risk patients with primary stage II/III breast cancer were treated with high-dose chemotherapy comprising etoposide, ifosfamide, carboplatin and epirubicin (VIC-E). Tumor cells of epithelial origin were analyzed using the monoclonal antibodies CK2 (IgG1) and A45-B/B3 (IgG1) against cytokeratin (CK) components in bone marrow (BM) aspirates prior to chemotherapy, and in peripheral blood stem cell transplants (PBSCT). They were separated after the first (21/21 patients) and the second cycle (16/21 patients) of induction chemotherapy with VIP-E (etoposide, ifosfamide, cisplatin, epirubicin). Preliminary results showed CK positive tumor cells in 40% (14/35) of the analyzed transplants. In 7/12 (58.3%) patients, CK positive tumor cells were detectable in BM prior to treatment. Sixteen patients were separated after the 1st and 2nd cycle of VIP-E. PBSCT of 14/16 patients were assessable for presence of CK positive tumor cells. Our preliminary results demonstrate a lower tumor cell contamination of PBSCT separated after the 2nd cycle of induction therapy (14.3%) compared to contamination after the first induction therapy (64.3%). To date, 4/21 patients have experienced a relapse, and three of these patients had tumor cell positive transplants. Due to the small patient number only a trend towards a superior relapse-free survival in the patient group with CK negative transplants can be shown by Kaplan-Meier analysis.