To determine whether the suprachiasmatic nuclei (SCN) of the house sparrow exhibit circadian variations in activity, metabolism within these and several other diencephalic structures was studied using the 2-deoxyglucose (2-DG) method at several times of day. Uptake of 2-DG was high at midday and mid-subjective day, but low at midnight within the SCN. Uptake was high at midday and low at midnight and mid-subjective day within the ventral lateral geniculate nucleus and lateral anterior nucleus, while no daily or circadian variation was observed within the periventricular preoptic nucleus. These data indicate that the avian SCN, as in mammals, express circadian rhythmicity.