To determine the accuracy of the ultrasonographic measurement of ulnar nerve to cubital tunnel area for diagnosis of ulnar neuropathy at the elbow.Patients with confirmed ulnar neuropathy at the elbow and normative, healthy volunteers were evaluated with high-resolution ultrasound. The cross-sectional areas (CSAs) of the ulnar nerve and cubital tunnel were measured with the elbow extended and flexed, and results from the 2 groups were compared.Electromyography laboratory and radiology department of a tertiary care center.Twenty-seven patients with ulnar neuropathy at the elbow and 20 controls.Not applicable.The ratio of ulnar nerve to cubital tunnel CSA with the elbow flexed.The ulnar nerve, with the elbow flexed, was larger in those with ulnar neuropathy at the elbow, and this group also had larger cubital tunnels than did controls. In those with ulnar neuropathy at the elbow, the ratio of the ulnar nerve to cubital tunnel was .31, and in the controls it was .32, which was not significantly different (P=.89).The ratio of ulnar nerve to cubital tunnel did not differentiate those with ulnar neuropathy at the elbow from controls.