Obesity and atherosclerosis, and their consequences, including cardiovascular disease, are plagues of the 21st century. Chronic inflammation, whose mechanism is not well understood, underlies the pathophysiological bases of both processes. T lymphocytes, macrophages, and the proinflammatory cytokines produced by these cells play key roles in the immunological disturbances accompanying obesity and atherosclerosis. It was recently shown that T-regulatory cells can play a role in these processes. T-regulatory cells are a small subpopulation of T cells which are responsible for inhibition of the immune response. In this review, experiments conducted in mice and human models on the role of diminished number and/or function of T-regulatory lymphocytes in the pathogenesis of immune disturbances accompanying obesity and atherosclerosis are discussed. The results of studies using T-regulatory cells to stabilize and decrease atherosclerotic lesions in blood vessel walls are also summarized. The results of experiments performed so far are encouraging and give some hope for the future use of T-regulatory cells in the therapy of obesity and atherosclerosis.