Contribution of one case of a 24-year-old patient, with a renal graft, who was diagnosed with vesical leyomiosarcoma. Radical cystectomy with ureterosygmoidostomy was performed. The rarity of vesical sarcoma, both in normal population or among those undergoing transplantation, as well as the greater tendency of transplanted patients to suffer malignant neoplasia, are emphasised.