The present invention relates to a method for treating prostate cancer, which comprises administering an anti-CTLA4 antibody, or an antigen-binding portion thereof, especially a human antibody against human CTLA4, such as antibodies 3.1.1, 4.1.1, 4.8.1, 4.10.2 , 4.13.1, 4.14.3, 6.1.1, ticilimumab (also known as 11.2.1), 11.6.1, 11.7.1, 12.3.1.1, 12.9.1.1, and ipilimumab (also known as MDX-101 and 10D1) , in combination with hormone therapy. Hormone therapy agents include, inter alia, antiandrogens (e.g., megestrol, cyproterone, flutamide, nilutamide, and bicalutamide), GnRH antagonists (e.g., ababa Rick and histrelin), and LH-RH agonists (eg, leuprolide, goserelin, and buserelin). The present invention relates to neoadjuvant therapy, adjuvant therapy, treatment of elevated PSA, first-line treatment, second-line treatment and third-line treatment of localized or metastatic prostate cancer.