This guide summarizes clinical evidence comparing the effectiveness and safety of treatments for clinically localized prostate cancer. It discusses expectant management and three active treatments (radical prostatectomy, radiation therapy, and hormonal therapy). This guide does not cover nutritional supplements. It also does not cover some newer treatments (cryotherapy, high-intensity focused ultrasound, and laparoscopic or robotic-assisted prostatectomy) for which there is little research about comparative effectiveness. This guide does not address strategies to prevent or screen for prostate cancer or strategies to treat advanced prostate cancer.