After radical prostatectomy for clinically localized prostate cancer, biochemical progression is seen in up to 40% of the patients due to persistent local and/or systemic remnants. Isolated disseminated carcinoma cells, undetectable by current staging methods, are of special interest as potential precursors of subsequent overt metastases. In the present study, immunohistochemistry (IHC) was performed to evaluate simultaneously the frequency of occult carcinoma cells in both lymph nodes (LNs) and bone marrow (BM) obtained from the iliac crests of 45 prostate cancer patients with untreated stage T(1-3) pN0 M0 prostatic carcinoma. IHC using monoclonal antibodies (MAbs) against epithelial cytokeratins was performed on 521 paraffin-embedded LNs histopathologically classified as tumorfree (pN0), as well as on BM cytospin preparations. To confirm the prostatic origin of positive cells in LNs, additional IHCs for prostate-specific antigen (PSA) and epithelial glycoproteins were performed. In total, isolated tumor cells in LNs and/or BM were detected in 17 of the 45 patients. Parameters such as tumor stage, grade and volume of the primary tumor as well as blood serum PSA levels could not detect patients harboring disseminated single tumor cells in LNs or BM. Following a median observation time of 24.9 months, no significant correlation between IHC positivity and PSA progression as a measure of early relapse was observed. Although the overall incidence of occult tumor cell spread corresponds to similar incidence of relapses after radical prostatectomy as reported by others, the fate of these cells needs to be evaluated in longer follow-up studies.