Purpose We examined the intracystic flow pattern and portal hemodynamics with Doppler sonography in patients with Caroli's disease. Methods Sonographic characteristics and portal hemodynamics were studied by color Doppler sonography and spectral analysis in 5 patients (4 children and 1 adult) with Caroli's disease using high-frequency transducers. Caroli's disease was associated with infantile polycystic kidney disease in 4 patients and congenital hepatic fibrosis in 2 patients. Four patients had no clinical or imaging evidence of portal hypertension. The adult patient had congenital hepatic fibrosis and portal hypertension. Results Color Doppler sonograms and spectral analyses disclosed distinctive hepatic arterial and portal venous flow within the fibrovascular projections in the bile ducts of all the children. The adult with advanced portal hypertension presented with a no-flow state in the intracavitary part of the portal vein and a strong arterial signal related to disturbed hemodynamics in the arterialized liver. Conclusions The fact that portal hemodynamics change over time should be taken into account when Doppler assessment of Caroli's disease is attempted. Doppler sonographic monitoring of the portal system to indirectly diagnose and follow the progression of so-called congenital hepatic fibrosis may be an effective alternative to liver biopsy. © 1998 John Wiley & Sons, Inc. J Clin Ultrasound 26:283–287, 1998.