Light and electron-microscope studies of the smooth muscle of the gizzard and its innervation in the chick and the pigeon have been made. The muscle is organised into extensive interlocking bundles, with frequent anastomoses between adjacent bundles. Nexuses are common between apposing smooth muscle cell membranes. The innervation of the smooth muscle is comparable to that in other gastrointestinal circular muscle. These results are discussed in regard to the contractility and electrophysiology of the tissue.