Objective— Peroxisome proliferator-activated receptor γ (PPARγ) ligands reduce lesion formation in animal models of atherosclerosis by mechanisms that have not been defined completely. We hypothesized that PPARγ ligands stimulate endothelial-derived nitric oxide release (·NO) to protect the vascular wall. Methods and Results— The PPARγ ligands, 15-deoxy-Δ 12,14 -prostaglandin J 2 (15d-PGJ 2 ) or ciglitazone, stimulated a PPAR response element-luciferase reporter construct in transfected porcine pulmonary artery endothelial cells (PAECs), demonstrating that PPARγ was transcriptionally functional. Treatment with 15d-PGJ 2 or ciglitazone significantly increased release of ·NO from PAECs or human aortic endothelial cells and augmented calcium ionophore–induced ·NO release from human umbilical vein endothelial cells measured by chemiluminescence analysis of culture media. Increases in ·NO release caused by treatment with 15d-PGJ 2 occurred at 24 hours, but not after 1 to 16 hours, and were abrogated by treatment with the transcriptional inhibitor α-amanitin. Overexpression of PPARγ or treatment with 9-cis retinoic acid also enhanced PAEC ·NO release. Neither 15d-PGJ 2 nor ciglitazone altered eNOS mRNA, whereas 15d-PGJ 2 , but not ciglitazone, decreased eNOS protein. Conclusions— Taken together, these findings demonstrate that PPARγ ligands stimulate ·NO release from endothelial cells derived from multiple vascular sites, through a transcriptional mechanism unrelated to eNOS expression.