Peroxisome proliferator activated receptor (PPAR) gamma is an orphan member of the nuclear hormone receptor superfamily and is expressed at high levels specifically in adipose tissue. Recent data suggest that this factor is a central regulator of adipocyte gene expression and differentiation. Fibroblastic cell lines that express PPAR gamma ectopically can be induced to differentiate into fat cells by a variety of lipids and lipid-like activators of PPARs, suggesting that this protein may function to link adipogenesis with systemic lipid metabolism.