OBJECTIVE We sought to evaluate the sensitivity and specificity of transcranial color-coded duplex sonography (TCCS) and the effect of an ultrasonographic contrast agent in the long-term surveillance of intracranial aneurysms treated with Guglielmi detachable coils. METHODS Forty-six studies were obtained in patients with intracranial aneurysms treated with coils. All studies were obtained within 2 months of surveillance digital subtraction angiograms, which was adopted as the standard for observing aneurysm refilling. For 34 of the studies, imaging was performed both before and after infusing an ultrasonographic contrast agent (Levovist). The remaining 12 studies were unenhanced. Aneurysms were described either as being fully occluded or as having residual flow. The degree of residual flow was quantified as minor, moderate, or extensive. The operator was blinded to the results of digital subtraction angiography during TCCS assessment. RESULTS TCCS correctly identified 19 of 20 aneurysms with complete occlusion (sensitivity, 95%; specificity, 84%). TCCS also identified all 16 of the clinically relevant aneurysms with either moderate or extensive residual flow visualized on digital subtraction angiograms and 5 aneurysms only after contrast enhancement (sensitivity, 100%; specificity, 97%). The overall accuracy of TCCS in identifying clinically relevant aneurysms was 85% without contrast enhancement and 96% with contrast enhancement. CONCLUSIONS Contrast-enhanced TCCS shows promise as a noninvasive imaging method for the surveillance of coiled intracranial aneurysms.