Septal destruction and ovariectomy each influenced food intake and body weight differentially. Animals sustaining septal damage ingested significantly more food than the other groups, and septal hyperphagia persisted for as long as 109 days. Ovarian hyperphagia did not occur under conditions of constant illumination. Septal destruction exerted essentially no effect on body weight, while ovariectomy substantially increased body weight. Sequential surgical manipulations provided further evidence that the ovaries and the septum influence food intake and body weight via independent mechanisms. Results indicated that the septal and ovarian effects on water intake are not mediated via independent mechanisms. Septal and ovarian hyperdipsia were found to be very robust effects occurring regardless of the lighting regimen. It was further demonstrated that ovarian hyperdipsia is not secondary to food intake but rather is primary hyperdipsia.