Intraperitoneal injections of either cyclic AMP or dibutyryl cyclic AMP are capable of producing a wave of autophagy in rat liver which resembles closely that stimulated by glucagon. These autophagic vacuoles are acid-phosphatase-positive and appear to arise via the envelopment of organelles by double-walled cisterna. At later times these autophagic vacuoles are usually surrounded by a single membrane. Injection of equimolar amounts of 5'-AMP failed to produce a wave of autophagy. These findings constitute preliminary evidence that glucagon-stimulated autophagy is mediated at least in part by cyclic AMP.