The expression of dbp, a putative clock-controlled transcription factor, was investigated in the mouse brain by in situ hybridization using antisense cRNA probe. Positive dbp mRNA signals were detected in various parts of the brain, with the highest expression in the suprachiasmatic nucleus (SCN). The circadian expression profile was investigated in SCN and extra-SCN areas. In the SCN, dbp mRNA signals showed a peak at early daytime (ZT/CT4) and a trough at early nighttime (ZT/CT16) in both light-dark and constant dark conditions. In the cerebral cortex and the caudate-putamen, dbp mRNA was also expressed in a circadian manner, but the phase of dbp mRNA expression in these structures showed a 4-8 hr delay compared to that in the SCN. These findings indicate that the circadian expression profile of dbp in the extra-SCN brain areas is different from that in the SCN.