OBJECTIVES:To evaluate health related quality of life (HRQOL) using the Medical Outcomes Study 8-items Short Form Health Survey (SF-8) questionnaire in Japanese patients with early prostate cancer. METHODS:A cross-sectional analysis was done in 457 patients with prostate cancer treated with radical prostatectomy, external beam radiotherapy, brachytherapy, androgen deprivation therapy, and watchful waiting or a combination these therapies. General HRQOL was measured using the Japanese version of the SF-8 questionnaire and disease-specific HRQOL was assessed using the Japanese version of the Extended Prostate Cancer Index Composite. RESULTS:The external beam radiotherapy group reported significantly lower values for the physical health component summary score (PCS) in comparison to the radical prostatectomy and brachytherapy groups (P < 0.05). In the analysis of both the PCS and the mental health component summary score (MCS) over time after treatment, higher scores with time were found in the radical prostatectomy group. No significant change over time after androgen deprivation therapy in the PCS was found. In contrast, the MCS was found to deteriorate in the early period, showing a significant increase over time. CONCLUSIONS:SF-8 in combination with the Extended Prostate Cancer Index Composite has shown to be a helpful tool in the HRQOL assessment of Japanese patients treated for localized prostate cancer.