Background: Sonography is a sensitive, noninvasive method that can be used to detect regional lymph node metastases. Color Doppler sonography (CDS) can supply further information on lymph node perfusion. Objective: We evaluated the usefulness of CDS for differentiating between benign lymphadenopathies and lymph node metastases of cutaneous melanoma. Methods: In a prospective study, reactive inflammatory lymph nodes (rLN) and lymph node metastases of cutaneous melanoma (mLN) were examined by sonography and CDS. Lymph node echogenicity and shape (length/depth ratio) were determined by sonography. The vascularization pattern of the lymph nodes was established with CDS. We recorded the Doppler frequency spectra at the hili of the lymph nodes and then calculated the resistance and pulsatility indices (RI, PI). Results: The echogenicity of the lymph node centers had a sensitivity of 96% and a specificity of 100%. The shape differed highly significantly between the two groups (P < .001). The criterion length/depth ratio < 2 had a sensitivity of 85% and specificity of 86%. Hilus vessels could be detected in 14 of 22 rLN (64%). These vessels, however, were not present in any of the metastases. The RI and the PI in detectable lymph node vessels differed between the two groups (RI: P < .05; PI: not significant), but because of the overlap between the two groups, these indices were of no diagnostic value. In the presence of 2 or more of the following 3 criteria: length/depth ratio < 2, hypoechoic center, and the absence of hilus vessels, diagnosis of metastasis of malignant melanoma had a sensitivity of 100% and a specificity of 96%. Conclusion: CDS improves the diagnostic accuracy of conventional sonography. The measurement of Doppler curves in lymph node vessels and the calculation of pulsatility and resistance indices, on the other hand, is time-consuming and seems to be of no diagnostic value. (J Am Acad Dermatol 1999;41:703-9.)