Rev-Erbalpha (NR1D1) is an orphan nuclear receptor encoded on the opposite strand of the thyroid receptor alpha gene. Rev-Erbalpha mRNA is induced during adipocyte differentiation of 3T3-L1 cells, and its expression is abundant in rat adipose tissue. Peroxisome proliferator-activated receptor gamma (PPARgamma) (NR1C3) is a nuclear receptor controlling adipocyte differentiation and insulin sensitivity. Here we show that Rev-Erbalpha expression is induced by PPARgamma activation with rosiglitazone in rat epididymal and perirenal adipose tissues in vivo as well as in 3T3-L1 adipocytes in vitro. Furthermore, activated PPARgamma induces Rev-Erbalpha promoter activity by binding to the direct repeat (DR)-2 response element Rev-DR2. Mutations of the 5' or 3' half-sites of the response element totally abrogated PPARgamma binding and transcriptional activation, identifying this site as a novel type of functional PPARgamma response element. Finally, ectopic expression of Rev-Erbalpha in 3T3-L1 preadipocytes potentiated adipocyte differentiation induced by the PPARgamma ligand rosiglitazone. These results identify Rev-Erbalpha as a target gene of PPARgamma in adipose tissue and demonstrate a role for this nuclear receptor as a promoter of adipocyte differentiation.