A positive diagnosis of urinary stone was made in 183 of 407 patients (44.9%) with renal colic seen in the emergency room. 182 (44.7%) had normal intravenous pyelograms, 26 (6.4%) had evidence of dilatation of the urinary system, possibly due to the passage of a stone, and 16 (3.9%) had other pathological urinary conditions, such as double collecting system or cysts. Stones were located in the upper urinary tract in 28.4%, in the midureter in 21.9%, and in the lower ureter in 49.7%. There was a statistically significant correlation between recurrent episodes of left-sided renal colic, erythrocytes in the urine and the presence of a stone in the urinary tract. No ethnic differences were found, nor was there a difference in the rates of stones found in those who were hospitalized and in those who were not.