1. Gap junctions and junction-mediated cell-to-cell communications are obligatory features of gland cells, whatever their secretory product is. 2. Studies on pancreatic islets and acinar cells indicate that cell-to-cell communication via gap junction channels is required for proper biosynthesis, storage and release of both insulin and amylase. 3. However, the endocrine and exocrine portions of the pancreas show opposite connexin (Cx) and coupling changes in relation to the activation and inhibition of their secretory functions. 4. These differences may be accounted for by the expression of Cx43 in pancreatic islets and of Cx26 and Cx32 in pancreatic acini. This alternative expression of connexin isoforms is also found in several other endocrine and exocrine glands. 5. These observations indicate that connexin-made channels play a central role in the control of secretory events.