To determine the potential risk of hematogenous dissemination of prostate cancer cells during radical prostatectomy (RP), we investigated the pre- and intraoperative circulating prostate-specific antigen (PSA) mRNA in patients with clinically localized prostate cancer, with special reference to neoadjuvant hormonal therapy (NHT). Using a nested reverse transcriptase (RT) polymerase reaction (PCR) assay, PSA mRNA in the peripheral blood was evaluated pre- and postoperatively in a total of 23 patients, 10 of whom received NHT with antiandrogens. The RT-PCR assay employed detected one LNCaP cell in 10(7) mononuclear blood cells, and showed no positive signal in the blood samples from all 15 healthy controls. Pre- and intraoperative circulating PSA mRNA was positive in 11 (48%) and 18 patients (78%), respectively. All 11 patients with positive preoperative PSA mRNA continued to be positive during RP, and seven (58%) of 12 patients with negative preoperative PSA mRNA had a positive conversion. Although the patients' ages, preoperative serum PSA values and clinical or pathological stages were not associated with the pre- and intraoperative PSA mRNA results, the NHT group showed a significantly lower incidence of preoperative PSA mRNA positivity (2/10) than the group receiving RP alone (9/13) (20% vs 69%, P = 0.036). NHT, however, showed no suppressive effect on either intraoperative positivity or positive conversion of circulating PSA mRNA. The present study suggests that a substantial number of patients receiving RP are at risk of hematogenous dissemination, and NHT with antiandrogens has a minimal or no suppressive effect on the circulating PSA mRNA during surgical manipulation of the prostate. Because the clinical significance of circulating cancer cells remains to be determined, long-term follow-up in association with the circulating cancer cells assessed by the RT-PCR is essential in order to establish the role of molecular staging as well as NHT.