To assess the association of S447X mutation and Hind III polymorphism in the lipoprotein lipase gene with dyslipidemia of the metabolic syndrome in patients with essential hypertension. A total of 983 patients were randomly selected from those with hypertension (diagnosed in the Community-based Comprehensive Studies on Prevention and Control of Hypertension Project in China) and those not treated with anti-hypertensive medications for at least in 2 weeks immediately before blood collection. Among them were 389 subjects with dyslipidemia and 594 subjects without dyslipidemia. The definition of dyslipidemia in patients with hypertension was used only when triglyceride or HDL-cholesterol was at abnormal level. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to determine Ser447stop mutation and Hind III polymorphism in LPL gene. Linkage disequilibrium between the two sites was observed, with three major haplotypes identified: H+S, H-S, and H-X. The LPL gene S447X mutation an