Adipocytes produce the endothelial-cell specific molecule-1 (ESM-1), which inhibits leukocyte adhesion and migration through the endothelium. This study investigates ESM-1 expression and regulation in human adipose tissue. Subcutaneous abdominal adipose tissue was obtained from seventy postmenopausal women. Fourteen women subsequently underwent non-pharmacological weight reduction. In vitro experiments were performed on adipocytes isolated from human mammary adipose tissue. We determined gene expression by TaqMan RT-PCR and measured ESM-1 levels in serum and cell culture medium by ELISA. Mature adipocytes produced ESM-1. ESM-1 gene expression was higher in adipocytes than in preadipocytes. Cortisol inhibited ESM-1 gene expression in preadipocytes. Insulin and cortisol inhibited adipocyte ESM-1 production in adipocytes. This inhibitory effect of insulin was attenuated by insulin resistance, as ESM-1 gene expression in subcutaneous adipose tissue was increased in obese, hyperinsulinemic women. In contrast, ESM-1 serum levels were reduced in obese women and inversely correlated to C-reactive protein levels. Five percent weight loss did not markedly change gene expression. Circulating ESM-1 levels increased significantly, albeit modestly. ESM-1 is actively produced by adipocytes. However, since ESM-1 adipocyte gene expression and circulating plasma levels are not correlated, other sources of ESM-1 may be more important. Circulating ESM-1 levels are reduced in the overweight and obese, consistent with the notion that ESM-1 may play some role in obesity-associated vascular disease.