This review article aims to overview modern prostate brachytherapy in Japan. Permanent transperineal prostate brachytherapy with I-125 started in September, 2003 in Japan. Brachytherapy has several advantages: the dose is adapted precisely to the tumor shape and size, and the long-lived isotope gives a higher tumor dose with less damage to normal tissue; less-time consuming for patients and staff: long-term results comparable to surgery or external beam series in the USA; and quality of life after brachytherapy also appealing. These advantages have brought about increasing use in Japan as well. Patients with a high probability of organ-confined disease and a low-risk group are appropriately treated with brachytherapy. Brachytherapy candidates with a significant risk of extraprostatic extension should be treated with supplemental external beam radiation therapy. High-dose-rate (HDR) brachytherapy with Ir-192 has preceded seed implants in Japan. HDR has some theoretical advantages. Long-term results of brachytherapy in the USA are comparable with surgery or external beam irradiation so far. We should develop more sophisticated brachytherapy techniques in Japan.