Research regarding the treatment of metastatic prostate cancer has been undergoing dramatic progress. Treatment of hormone-naïve metastatic prostate cancer includes surgical castration and medical castration that lowers androgen level in the blood using drugs. Although these androgen deprivation therapies are very effective, hormone-naïve metastatic prostate cancer finally leads to castration-resistant prostate cancer because resistance to surgical or medical castration occurs. The treatment at this stage includes not only docetaxel, but also new androgen synthesis inhibitor or androgen receptor inhibitors such as abiraterone or enzalutamide, new cytotoxic anticancer agents such as carbazitaxel, and radioisotope treatment such as radium-223. Recently, studies on the effect of chemotherapy on hormone-naïve metastatic prostate cancer before the development of castration-resistant prostate cancer have been actively published. As a result, various guidelines have recommended docetaxel as the first-line therapy for hormone-naïve metastatic prostate cancer. In this manuscript, we will summarize the basic concepts of androgen deprivation therapy for hormone-naïve metastatic prostate cancer and the main results of research on chemotherapy for hormone-naïve metastatic prostate cancer.