We detected micrometastatic prostate cancer cells in lymph nodes and bone marrow using reverse transcriptase-polymerase chain reaction (RT-PCT) specific for prostate-specific antigen (PSA). RT-PCR revealed PSA mRNA in two lymph nodes obtained from two patients with negative histological and immunohistochemical analyses for lymph node metastases. Of 26 patients with negative bone scan imaging, 7 had PSA mRNA detected in the bone marrow by RT-PCR. The RT-PCR will be a relevant tool to allow a more accurate clinical assessment of lymph node and bone metastases in patients with prostate cancer.