The gallbladder and the biliary tract of 85 neonates were sonographically examined, in the fasting state. The gallbladder was detectable in all neonates and showed a measurable contraction. Two types of biliary contraction could be observed: a concentric contraction of length, depth and width (concentric type) or a contraction of depth and width (collapse type). The grade of postprandial contraction was independent of the level of serum bilirubin. Furthermore, sonographic criteria were established allowing the differentiation of the bile ducts and their discrimination from hepatic arteries.