The aim of this work was to report some case histories on the usefulness of spiral TC, used for several years both to diagnose renal colic and urinary lithiasis and to study radio lucent stones that are often difficult to be detected with traditional radiology. 13 patients, aged between 31 and 76 (average age: 54.2), were therefore examined. Eight of them had a ureteral colic when examined, while five patients had shown symptoms some days before being hospitalised in our ward. In all cases, ultrasonography showed a significant hydronephrosis, while direct radiography of the urinary tract could not detect any images that could be associated with radio-opaque lithiasis. All patients therefore underwent an abdominal spiral TC with no contrast medium within 24 hours after hospitalisation. The confrontation between the results obtained by ultrasonography and those obtained by spiral TC, showed the usefulness of the former method to detect stones located in the proximal ureter or in its intramural tract, while the latter could detect the lithiasis of the proximal ureter in 3 cases (23%), of the mid ureter in 2 cases (15.3%), and of the distal ureter in 8 cases (61%). The stones had, approximately, a 5 mm diameter in 5 cases. In 6 cases the diameter was between 6 and 10 mm, and more than 1 cm in 2 cases. Both methods proved to be equally accurate in the assessment of the hydronephrosis degree and of the thickness of the renal parenchyma. The therapy was medical in 2 cases and open surgery in 3 cases, while 8 patients were treated with ureterolitholapaxy with a ballistic searcher. The usefulness of TC in the study of urolithiasis nowadays is supported by a large literature which clearly supplies with documentary evidence the high sensitivity and specificity of such a method in diagnosing the presence of urolithiasis in general and above all of ureteric stones. Such a method not only makes an accurate evaluation of the stones location possible, but it can also assess the calculi dimensions and the indirect signs of the functionality of the kidney affected, without having to use the contrast medium. This method needs very limited execution times and allows a diagnostic of possible collateral pathologies. The main disadvantage of spiral TC, if compared to conventional radiology, is that the patient is exposed to a larger quantity of ionizing radiations, although such an inconvenience will be overcome by the new and more technologically advanced machines. According to our experience, though based on a limited number of cases, spiral TC allowed us to get a quick diagnosis of radio-lucent lithiasis, to see the seat and dimensions of the calculi and finally to chose the most effective treatment. We can therefore think of a diagnostic protocol, for ureteral colics with hydronephrosis or complicated by hyperpyrexia or sepsis, with spiral TC in order to have a quick diagnosis and start the most effective therapy in case an ultrasonographic research should not result diriment.