It is of clinical importance to control pain in the management of patients with endocrine-therapy-refractory prostate cancer. To evaluate factors influencing the manifestation of pain and the relationship between characteristics of pain and prognosis, patients with pain from bone metastasis were analyzed. A total of 48 patients with endocrine-therapy-refractory prostate cancer, who showed progression of bone metastasis and were followed-up until death, comprised the present study. The patients were divided into three groups according to the grade of pain: no need for analgesics, a need for non-opioid analgesics, and a need for opioid analgesics. The time interval between the diagnosis of the endocrine-therapy-refractory state and the requirement for analgesics was estimated. Survivals from the endocrine-therapy-refractory state were calculated according to the grade of pain or the time interval to requirement for analgesics. In addition, the extent of disease, the doubling time of tumor markers at the refractory state, any change of alkaline phosphatase, and other prognostic factors were examined in relation to pain. All 22 endocrine-therapy-resistant cases at initial treatment and 18 of 26 (69%) relapsed cases required analgesics during the clinical course until death. No difference in survival was observed between the grades of pain. The patients who needed analgesics within 1 year after becoming refractory to endocrine therapy showed significantly shorter survival than those without or with analgesics more than 1 year later. Although the time elapsing before analgesics were needed was not related to the extent of disease, the patients who showed a shorter doubling time for tumor markers and/or an exponential increase in alkaline phosphatase tended to require analgesics within 1 year. In endocrine-therapy-refractory prostate cancer, the early requirement for analgesics suggests poor prognosis, and the onset of pain may be attributable not to the extent of the disease but rather to the rapid expansion of bone metastasis.