Two cases of auto-transplantation of the kidney are presented. The first was carried out without prior planning during a ureterolysis procedure for retro-peritoneal fibrosis with a single kidney, by virtue of per-operative thrombosis of the renal artery. The second was used in the treatment of hypertension due to bilateral atheromatous renal artery stenosis with a lesion at the main bifurcation of the artery. In both these cases in which the surgical indication was related to the artery, the ureter was left intact. After 2 and 1 years respectively, the results are good. The important points of operative technique and tactics are emphasised. The order of the technique is important. It resembles that of homo-transplantation but in this case section and reimplantation of the ureter may be avoided. Preservation of the disconnected kidney is ensured by refrigeration with intra-arterial perfusion. Even if only for a short time, it consistently avoids the development of ischaemic tubulopathy. Ex-sito surgery, studied here in detail, is used in dealing with intra-hilar arterial lesions, tumours of both kidneys or a single remaining kidney, complicated cases of lithiasis etc. The results of the 100 known cases of renal auto-transplantation are analysed. They are good in 84 cases. The indications are discussed with regard to the different types of arterial, ureteral, neoplastic, traumatic and miscellaneous lesion.