Work reported over the past year has provided insights into the mechanisms whereby ligand activation of the nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR gamma) regulates systemic glucose and lipid homeostasis. PPAR gamma has also been implicated recently in the biology of monocytes and in cell-cycle regulation and cancer. Polyunsaturated fatty acids and eicosanoids bind and activate PPAR gamma, suggesting that these lipids may serve as hormonal regulators of a variety of biological processes.