One hundred thirty-three kidneys of 67 consecutive patients (one had prior unilateral nephrectomy) who underwent multidetector CT including noncontrast and arterial phase (acquired at 25 seconds from the start of 120 mL of intravenous contrast injection at a rate of 3 mL/s) scans were retrospectively evaluated. The detectability of renal calculi was determined by comparison of the noncontrast and contrast-enhanced scans.