Alpha-particle emitting radionuclides have recently obtained an increased attention when considering new strategies for treating disseminated cancer. Astatine-211(At211), that emits alpha particles is one among the most promising nuclides in this respect. In the PhD thesis by Jörgen Elgqvist (registered Medical Physicist) presented in this book At211 was used for evaluating the therapeutic efficacy, myelotoxicity, and radiation dosimetry in the treatment of intraperitoneally disseminated micrometastatic ovarian cancer in mice. In order to specifically irradiate the tumor cells At211 was labeled to monoclonal antibodies, targeting certain cell surface epitopes. The PhD thesis, presented on pages 1-148, received the Assar Gabrielsson Award in 2009 as "The best PhD thesis in cancer research from the University of Gothenburg during the past three years". In addition to the PhD thesis two animal studies are also presented in an appendix. The first study investigated the therapeutic efficacy with intraperitoneal alpha-radioimmunotherapy using different specific radioactivities. The second study invesigated the therapeutic efficacy using repeated alpha-radioimmunotherapy.