We developed selective monoclonal antibodies and used them for Western and immunocytochemical analyses to determine the tissue and cellular distribution of the human cyclic GMP-stimulated phosphodiesterase (PDE2). Western analysis revealed PDE2A expression in a variety of tissue types, including cerebellum, neocortex, heart, kidney, lung, pulmonary artery, and skeletal muscle. Immunocytochemical analysis revealed PDE2A expression in a subset of tissue endothelial cells. PDE2A immunostaining was detected in venous and capillary endothelial cells in cardiac and renal tissue but not in arterial endothelial cells. These results were confirmed by in situ hybridization. PDE2A immunostaining was also absent from luminal endothelial cells of large vessels, such as aorta, pulmonary, and renal arteries, but was present in the endothelial cells of the vasa vasorum. PDE2A immunostaining was detected in the endothelial cells of a variety of microvessels, including those in renal and cardiac interstitial spaces, renal glomerulus, skin, brain, and liver. Although PDE2A was not readily detected in arterial endothelial cells by immunocytochemistry of intact tissue, it was detected at low levels in cultured arterial endothelial cells. These results suggest a possible role for PDE2A in modulating the effects of cyclic nucleotides on fluid and inflammatory cell transit through the endothelial cell barrier.