Drosophila melanogaster is an ideal genetic model organism for circadian rhythms, which exhibits a great deal of circadian behavior, such as locomotor activity, feeding, eclosion and mating. Odors elicit a number of behavioral responses including attraction and repulsion in Drosophila. The previous data show that the electrophysiolgical responses, that is electroantennogram (EAG), to odorants display a robust circadian rhythm. However, so far, there is no report that olfactory behavior displays a circadian rhythm in Drosophila, and where is the locus of the rhythm pacemaker. By using a T-maze apparatus, we show that wild-type Drosophila melanogaster exhibits a robust circadian rhythm in the olfactory attractive and repulsive responses under 12h:12h light-dark cycle. These responses were lower during the day and began to rise at early night, peaking at about the middle of the night, and then declining thereafter. Under constant dark, the wild-type displays a circadian pattern similar to that in olfactory response under LD. The olfactory rhythms in attractive and repulsive behavior, which appear to be in phase with each other, are in different phase with locomotor activity. This suggests that the response rhythm is independent of locomotor activity. The olfactory response rhythms were lost in period or timeless mutant flies (per~0, tim~0), indicating clock genes control circadian rhythms of olfactory behavior. The rhythms in olfactory response persisted in the absence of the pigment-dispersing factor (PDF) neuropeptide or the central pacemaker lateral neurons (LNs) known to drive circadian patterns of locomotion and eclosion. These results indicate that the circadian rhythms in olfactory behavior in Drosophila are driven by the pacemakers which do not control the rest-activity cycle and are likely in the antennae.