Sonographic detection of ureteral jets entering the urinary bladder is a well known procedure. Color Doppler ultrasound was used to image the ureteral jets in 28 patients with unilateral ureteral calculi proved by intravenous urography. Three major findings of ureteral jets were obtained in the affected ureter with a stone : less frequency (26 patients), weak reflection (20 patients), and lower grade in length (27 patients)that were significantly different from the unaffected side in the same patient. No significant differences were found between the ureteral jets and the degree of hydronephrosis or the location of a stone. In conclusion, these results suggest that ureteral jets should be checked routinely during the procedure of color Doppler ultrasonogram in patients with possible unilateral ureteral obstruction. Color Doppler examination of ureteral jets may be an important adjunct in routine pelvic ultrasonogram especially in patients who have absolute or relative contraindications of intravenous urography.