This article reviews work that shows that the medial preoptic area of the hypothalamus plays a crucial role in controlling the occurrence of maternal behavior in rats. A primary goal of this report is to fit the medial preoptic area into a larger neural circuitry, examining its critical inputs and outputs. Lesions of the medial preoptic area disrupt maternal behavior and estradiol and prolactin injections into this region activate maternal behavior. The medial amygdala, which is located in the limbic telencephalon, sends a neural projection to the preoptic region. Research indicates that this projection influences maternal behavior by relaying olfactory input to the medial preoptic area. The output of the preoptic area influences maternal behavior through descending projections to the brain stem. One of the influences of such projections might be to regulate neural circuits involved in controlling specific maternal responses, such as retrieval (carrying of pups) behavior.