Obesity is likely to become a major worldwide epidemic in the 21st century. Clinical evidence demonstrates exaggerated inflammatory responses and an enhanced tissue injury in obese subjects with cardiovascular disease, sepsis, thrombosis and allergic diseases. Emerging evidence suggests that obesity per se is associated with a systemic inflammatory response that is characterized by endothelial cell dysfunction, oxidative stress, and the activation of circulating immune cells. A large number of cytokine-like substances (adipokines) produced by adipose tissue have been implicated in the systemic inflammatory response associated with obesity. Insulin resistance also appears to contribute to the inflammatory phenotype observed in obesity. There is emerging evidence from experimental and clinical studies that implicate the microvasculature as a major target for the deleterious effects of obesity-induced inflammation, and that the altered microvascular responses underlie the exaggerated injury responses to cardiovascular disease, sepsis, thrombosis and allergic diseases in obese subjects.