We have previously reported on the value of transvaginal color Doppler evaluation of the ureteral jets to confirm ureteral patency. In this study, we attempt to validate the simple and widely available gray-scale ultrasound technique to perform the same task. Fifty consecutive patients without a history of urinary complaints were recruited. The presence or absence of the right and left ureteral jets was registered using gray-scale imaging, comparing the technique to color Doppler as the 'gold standard'. The time to the detection of the first jet as well as the total scanning time were documented for each side. The jets were seen with equal frequency on both the right and the left sides (34 observations each). In 24 patients, both jets were visualized. The median time to detection of the first jet was 47 s (range 34-79 s) for the right jet and 53 s (36-84 s) for the left jet (p = 0.42). The median total scanning time was 176 s (139-259 s). Gray-scale imaging was associated with a sensitivity of 68% and a positive predictive value of 100%. Although color Doppler results may be more attractive because of their impressive color-coded appearance, the major disadvantage of this technique is that it requires sophisticated and costly equipment. Transvaginal gray-scale imaging is a reliable and useful test for the detection of ureteral jets in the bladder. It can be used as a first-line diagnostic tool, particularly in settings where color Doppler is not available. Its benefits include safety, low cost, convenience and simplicity. With a positive predictive value of 100%, this test may be used in the postoperative patient, especially when ureteral patency is in question.