The application of UCAs to the kidney is still in its infancy; however, there are several areas of great promise. UCAs may replace CT in complex renal cyst evaluation and follow-up, eliminating the need for costly CT scans with their attendant potential contrast nephrotoxicity. This approach may decrease patient and physician uncertainty and improve diagnostic confidence. The use of UCAs is likely to be clinically useful in the evaluation of the indeterminate small renal mass on CT or MR imaging. Another probable useful application will be in renal artery stenosis. Routine application of UCAs may increase the percentage of diagnostic examinations, increase diagnostic confidence, and decrease examination times. It also will likely become the first line of evaluation in pyelonephritis, and be useful in immediate assessment of residual tumor after radiofrequency ablation. Of course, substantial additional work needs to be performed in large groups of patients to prove this currently optimistic outlook.