The metabolic syndrome is a syndrome characterized by visceral obesity, and is associated with lipid abnormalities, hypertension, and hyperglycemia. The prevalence of this syndrome is increasing in Japan, mainly because of widespread lifestyle changes. Studies from our and other laboratories have shown that early intervention with an ARB can attenuate the development of hypertension in animal models, with a similar trend found in the recent TROPHY clinical study. ARBs also cause inhibition of new-onset diabetes, and may have beneficial effects on insulin resistance and lipid metabolism. The results of multiple laboratory studies and clinical trials suggest that early intervention with ARBs will play an increasing role in preventing progression of the metabolic syndrome and its complications.