I. Introduction II. Protein Kinases in β-Cells: Expression and Characteristics A. Ca2+/calmodulin-dependent protein kinases B. Cyclic nucleotide-dependent protein kinases C. Ca2+/phospholipid-dependent protein kinases D. Mitogen-activated protein kinases E. Protein tyrosine kinases III. Phosphorylation of Endogenous Proteins in β-Cells A. Methods for studying protein phosphorylation in β-cells B. Endogenous kinase substrates in β-cells IV. Protein Kinases and the Regulation of Insulin Secretion A. Ca2+/calmodulin-dependent protein kinases B. Cyclic nucleotide-dependent protein kinases C. Ca2+/phospholipid-dependent protein kinases D. Mitogen-activated protein kinases E. Protein tyrosine kinases V. Protein Phosphatases and Protein Dephosphorylation in β-Cells A. Serine/threonine protein phosphatases B. Protein phosphatases in β-cells VI. Protein Kinase-Independent Secretory Pathways VII. Summary and Future Perspectives