Activators of peroxisome proliferator activated receptor (PPAR) regulate fatty acid metabolism and can induce adipocyte differentiation. We show here that the gamma subtype of PPAR is expressed at high levels in adipose tissue in contrast to a variety of other tissues, where little gene expression was noted. In addition, PPAR gamma is present at low levels in 3T3-L1 preadipocytes and is induced dramatically during adipocyte conversion using either normal differentiating conditions (fetal calf serum, dexamethasone, isobutyl-methylxanthine, and insulin) or the PPAR activator, WY-14,643. Thus PPAR gamma may be important for adipose cell development and function.