Objective: The advantages of non-contrast spiral computerized tomography (CT) were its accuracy and speed, no need for intravenously or orally administered contrast material and ability to detect extra-urinary system in the evaluation of acute flank pain. We assessed the use of spiral CT in-patients with acute flank pain and in patients with ureterolithiasis for prediction of a favorable clinical outcome. Methods: One hundred and eighty five patients having acute flank pain were evaluated with physical examination, urinalysis and hemogram, and non-contrast spiral CT. Stone size (greatest width-mm.), its localization, perinephritic fat stranding, the degree of hydronephrosis, tissue rim sign and perinephritic fluid were assessed on spiral CT. Extracorporeal shock wave lithotripsy (ESWL), surgical approaches, ureteroscopic stone extraction and conservative treatment were performed as therapeutic alternatives in urinary tract stone disease. Results: Urinary stone disease was determined in 173 patients (93.5%) out of 185 (mean age: 41.1 years) by non-contrast spiral CT. Stone localizations were kidney in 77 patients (59 unilateral, 18 bilateral) and ureter in 96 patients (94 unilateral, 2 bilateral). Spontaneous passage was assumed in 79 patients with ureterolithiasis. Only 38 patients spontaneously passed ureteral stones that were less than 7.4 mm. diameters. The greatest width difference was statistically significant between passed and unpassed group [(2.0-7.4 mm; mean 4.37$pm$1.63) vs. (4.0-10.0 mm; mean 7.35$pm$1.81), p