Comparisons between early daytime and early nighttime effects of 2-deoxy-D-glucose (2DG) injections on food and water intake and rectal temperature were made. Food intake was significantly enhanced by 2DG injections regardless of the phase of the light cycle. In the daytime, water intake was increased by a lower dose of 2DG (200 mg/kg, IP) but there was no further increase at a higher dose (400 mg/kg). At night, the lower dose of 2DG had no effect on water intake but the higher dose suppressed the water intake normally associated with feeding. Administration of 2DG reduced preprandial rectal temperature in a dose dependent fashion in both phases of the light cycle. However, preprandial rectal temperatures were decreased more at night than during the daytime after injection of the higher dose of 2DG. Therefore, 2DG-induced hypothermia is dependent on both the dose of 2DG injected and the phase of the light cycle in which glucoprivation is produced. Furthermore, below a certain level of body temperature, rats markedly reduced drinking behavior while maintaining but not increasing their feeding response to 2DG-induced glucoprivation. These results suggest that behaviors may be directed toward preservations of body temperature in preference to relief of hunger by eating and of thirst by drinking.