Retrograde infusions of ferritin into the canine pancreatic duct revealed accumulation of ferritin in a previously described periacinar space. Access to this space appeared to occur through minute disruptions of the cellular lining at the ductoacinar junction. Particulate material observed between acinar cells apparently extended from accumulations at the base of the cells. The periacinar space is bounded by the cell plasma membrane and the basal lamina of the acinar unit. The basal lamina appeared to permit diffusion of contents of the space into the interstitium where absorption occurred. In some cases following injection, disruption of the plasma membrane occurred, and zymogen granules were observed to mix with the infused fluid at the base of the cell. With more prolonged infusions at low pressures dilation of the ducts occurred along with focal intracellular areas of spheroid degeneration.