Percutaneous nephrostomy can be used to resect transitional cell carcinoma (TCC) from the renal pelvis, to avoid nephrectomy in selected patients. This procedure carries a potential risk of tumour seeding along the nephrostomy track, which it is our policy to irradiate prophylactically. A total of 25 procedures on 23 patients have been carried out since 1982. The 18 males and five females had a median age of 64 years (range 46-81) at the time of treatment. Of the ten patients with only one functioning kidney, nine had undergone contralateral nephroureterectomy, seven for TCC, one for a non-functioning kidney, and one for renal tuberculosis; one patient had received radical radiotherapy for an inoperable contralateral renal tumour. The other 13 patients had asked for a conservative treatment approach to be adopted. From 1982-1989, low dose rate 192Ir wire was used in 13 patients to deliver a median dose of 45 Gy (range 40-50) to the full length of the track at the surface of nephrostomy tube. Since 1989, we have used a high dose rate (HDR) 192Ir microSelectron to treat 12 patients with a single fraction of 10-12 Gy, including two who had undergone previously 192Ir wire track irradiation of the same kidney. One patient required a nephroureterectomy after developing a non-healing renal pelvis leak following combined modality treatment. Otherwise, no early or late radiation-related morbidity has been seen, and no nephrostomy track recurrences have occurred during a median follow-up of 5 years (range 1-9). The HDR microSelection has enabled us to deliver this treatment quickly and simply during the standard postoperative stay in hospital following percutaneous nephrostomy.