The paper presents the characteristics, the place and the limits of brachytherapy in prostate radiotherapy. While sparing the rectal wall, erectile function as well as urinary continence, I(125) and Pd(103) permanent implants represent interesting approaches for good prognosis tumours in comparison to surgery or conformal external beam radiotherapy with similar cure rates. Overcoming easily the problems of organ motion and patient positioning while allowing doses per fraction as high as 10 Gy, brachytherapy is an excellent boosting method in the treatment of intermediate or unfavourable prognosis tumours of which alpha/beta is 1,5 Gy. Encouraging biological control rates of 80-90% have been published in phase II trials. Compared to external beam radiotherapy, the heterogeneity of irradiation inside the clinical target volume should increase the probability of cure as for a specific dose, a significant part will be overdosed. So far, 120-130% of the prescribed doses are delivered to the peripheral zone at the origin of 70% of tumours. On the opposite, this heterogeneity is inducing an overdosage of the urethral bed at the price of higher toxicity levels in situations of previous obstructive syndrome and urethral stenosis. A better integration of the therapeutic modalities available, brachytherapy included, should increase our curative possibilities in the radiation treatment of prostatic cancer.