To establish the clinical significance of renal colic associated with extravasation of contrast material, the authors reviewed 158 consecutive patients who presented with renal colic-like symptoms at the William Beaumont Hospital Emergency Center over a four-month period. Forty-three patients were eliminated either because excretory urography was not performed or IVU did not show obstruction. Of the remaining 115 patients with "obstructive" IVUs, 21 (18 men, 3 women) or 18.3 per cent, were associated with contrast media extravasation of varying degrees. Patients with extravasation were compared with patients without extravasation by cross matching as to age, gender, and time of presentation. Extravasation patients demonstrated significantly less hydronephrosis, had smaller stones (1-5 mm) usually located at the ureterovesical junction, tended to pass their stones spontaneously, and required less hospitalization and one-third the number of manipulative procedures. There was no incidence of sepsis. The significance and future research implications of these findings are presented.