Small tumors of the mobile portion of the bladder may be treated by means of interstitial irradiation by iridium-192 wiring. Forty-four tumors (mostly T1, but also T2 and T3) were treated by this procedure and followed over five years. Good results are attained in 66 per cent of the cases. This method has the benefit of avoiding irradiation to the surgeon's hands, and of delivering to a specific site a dose of 6,000 rads. No bladder contraction was observed. Supplementary treatment by irradiation has to be considered in view of frequent recurrences of malignant bladder tumors after transurethral resection of partial cystectomy. In small cancers slightly infiltrating the bladder wall, many attempts have been made to replace tele-irradiation by interstitial irradiation. The latter delivers specifically high rad dosage to the involved area. Radium needles has been used in France by Darget before 1951 but evaluation of accurate dosage proved difficult. This material was dangerous to the surgeon's hands, and the procedure lead frequently to bladder sclerosis. This technique is currently used by Van der Werf-Messing in Rotterdam. She strongly advises preoperative tele-irradiation (3 X: 350 rads) to prevent tumor implants in the scar. An intravesical balloon filled with fluid radioisotope of gold-198 or cobalt-60 has been used for diffuse malignant papillary epithelioma. It was discontinued because of radiation cystitis and subsequent contraction of the bladder. Recently in well-limited tumors, Bloom and Wallace have used Tantalum-182 needles which have interesting physical properties (high energy and short half-life period) (2).