To investigate the cytoskeleton of the pancreatic acinar cells by electron microscopy, the pancreas of several species (dog, rabbit guinea pig, rat and mouse) was perfused with a mixture of a low concentration of glutaraldehyde and Triton X-100 via the pancreatic duct. After perfusion, the pancreas was fixed with 2.5% glutaraldehyde and processed for scanning and transmission electron microscopy. Scanning electron microscopy demonstrated that the water-soluble cytoplasmic matrices were successively removed by the detergent treatment. Transmission electron microscopy demontrated that without detergent treatment, the acinar cells had many secretory granules at the apical region, the nuclei were located at the base of the cell, and rough-surfaced endoplasmic reticulum and mitochondria throughout the cytoplasm. Microvilli were present at the luminal side and apical subplasmalemmal region showed a homogeneous appearance. With detergent treatment, the core filament in microvilli projected into the apical terminal web which attached to the junctional complex at the lateral membrane. Intermediate filamemts and microtubules were observed in the cytoplasm around the nuclei, and thin filaments were also found around the secretory granules.