The aim of this study was to determine the effect of excessive fructose intake on the development of the features of the metabolic syndrome and to test whether lowering the uric acid levels can prevent the development of these features. This randomized controlled trial included 74 adult men who were administered 200 g fructose daily for 2 weeks with or without allopurinol. Fructose ingestion induced a significant increase in fasting serum triglycerides, a decrease in HDL cholesterol, an increase in serum insulin and HOMA index, an increase in ambulatory systolic blood pressure and diastolic blood pressure, and an increase in body mass index. Fructose ingestion was also associated with an increase in fasting serum uric acid and allopurinol prevented its increase and at the same time blocked the increase in systolic and diastolic blood pressure. Moreover, the number of new cases of metabolic syndrome was dramatically reduced by allopurinol treatment (p<0.003). This was primarily explained by the effect of allopurinol in preventing the increase in blood pressure since allopurinol did not improve other features of the metabolic syndrome. Thus, these findings suggest a probable role of excessive fructose intake on the development of metabolic syndrome.