Seventeen patients with 19 lesions of focal nodular hyperplasia (FNH) underwent prospective examination with color Doppler ultrasound (US) and magnetic resonance (MR) imaging. In 13 lesions, color Doppler US demonstrated central spots with an arterial Doppler spectrum. The frequency shifts ranged from 1.02 to 1.94 kHz (mean, 1.56 kHz). On flow-sensitive unenhanced gradient-echo images, hyperintense central dots were depicted in only five of these 13 lesions. All the MR features of FNH were present in 12 lesions. Among the seven lesions without all of the MR features, central color spots were present with an arterial Doppler spectrum in four lesions. In the remaining three lesions, color Doppler examination demonstrated either peritumoral pulsatile flow (two lesions) or no flow (one lesion). Color Doppler US adds information about the intratumoral flow characteristics of this vascular malformative lesion and appears to be superior to MR imaging in detection of the arterial intratumoral abnormalities.