We make an evaluation of 66 ureteroscopies (URS) carried out in our Service over a period of 18 months. In 55 cases it was done for therapeutic purposes in ureteral lithiasis, and in 11 cases it was for diagnostic purposes. In the treatment of lithiasis resolutive effectivity at the first attempt was 68%, in 9% ureterolithotomy had to be performed due to the impossibility of approaching the calculus, and in 23% supplementary treatment was carried out by means of external litrotripsy. In the diagnostic field, effectivity was 72%. Notable complications arose in 6 cases (9%), 6 ureteral perforations, in three of which a urinoma was formed, all settled with a double J catheter. Open surgery was not resorted to in any case. No sequelae were observed and this technique therefore showed itself to be safe and effective.