The goal of radiation therapy is to deliver a high dose to the tumor while preserving normal surrounding tissue. For early-stage prostate cancer, the ultimate conformal irradiation is to place radioactive sources directly into the gland as permanent or temporary seeds. Contemporary prostate brachytherapy incorporates advances in computer analysis, imaging technology, and delivery apparatus, allowing exact and reproducible results. Accurate comparison of brachytherapy to surgery and external beam irradiation requires a randomized study. Comparisons of retrospective studies are fraught with the problems of the heterogeneous nature of early-stage prostate cancer. Pretreatment PSA and grade appear to be more sensitive variables than stage in predicting failure after irradiation. The treatment results based on biopsy are promising for the first two years. Brachytherapy may be considered as a therapeutic option: as monotherapy for early-stage disease and also as a boost following moderate doses of external beam irradiation for locally advanced disease.