Using an antibody revealed by the protein A-gold technique, we have studied the distribution of clathrin antigenic sites in the Golgi area of pancreatic B-cells. Golgi compartments showing an immunolabelling comprised extensive segments of cisternae, typical coated vesicles, dilated extremities of cisternae with condensing secretory material, and newly formed secretory granules. Most of the labelled membranes were observed at the trans Golgi pole while little immunoreactivity was found on the cis pole.