Recoverin, a retinal 23-kDa calcium-binding protein, serves as a calcium sensor in vision. The three-dimensional solution structure of calcium-free, myristoylated recoverin has been determined by multidnnensional heteronuclear magnetic resonance spectroscopy. The arnino-terminal mynstoyl group, critical for calcium-dependent membrane targeting, is sequestered in a deep hydrophobic pocket in the amino-terminal domain. The binding pocket is formed by a cluster of aromatic and other hydrophobic residues that are contributed by five flanking helices. This myristoyl binding pocket is likely to be a common structural element of EF-hand proteins possessmg calcrum-myristoyl switches.