After surgical removal of the neocortex and hippocampal formation, rats retained most of the movement patterns of locomotion, climbing, grooming, feeding, and fighting. However, forepaw immobility during swimming was abolished. Feeding behavior was suppressed temporarily but recovered partially. The distinctive postures of sleep and waking and a circadian rhythm of motor activity were retained. However, behaviors were often not performed at the appropriate time and place. The normal sequence of grooming behavior was disrupted; food hoarding and social behavior were essentially abolished. Removal of the neocortex alone had much the same effect as removal of neocortex and hippocampus together. Removal of hippocampus alone produced only a mild disruption of behavior. It is suggested that ascending nonspecific projections to the cerebral cortex play an important role in the moment-tomoment control of behavior but are not essential for the sleep-waking cycle.Naturalistic studies of animal behavior have usually emphasized careful description of motor patterns as a first step in the analysis of behavior (e.g., Tinbergen, 1972). Paradoxically, this phase of research has been neglected in laboratory studies of brain and behavior even though the laboratory offers many advantages favoring accurate observation. The importance of close attention to the details of movement and posture has been emphasized by recent evidence that the electrical activity of the hippocampal formation, the neocortex, and the reticular formation exhibits surprisingly detailed relations to concurrent motor activity (