An excretory role of pericanalicular vesicles was studied by following the uptake and transport of horseradish peroxidase in rabbit hepatocytes. The observations are interpreted to indicate uptake of horseradish peroxidase by pinocytotic vesicles which then move toward the biliary pole, thus becoming pericanalicular vesicles which discharge their contents directly into the bile canaliculi. With small loads, lysosomes other than multivesicular bodies are not involved in this route of transport. Although multivesicular bodies have also been shown to be active in the uptake of horseradish peroxidase from the sinusoidal surface, their subsequent fate is not known.