The associations between six genetic polymorphisms in the hepatic lipase (HL) gene (LIPC) and variation in postheparin HL activity and fasting serum lipoproteins were evaluated in 395 male Finnish coronary heart disease patients with HDL cholesterol concentrations </= 1.1 mmol/liter. The LIPC promoter polymorphism at position -514 was highly significantly associated with variation in HL activity (P = 0.0000008), with mean activities of 20.4, 17.5, and 13.2 mumol free fatty acid/ml per hour in subjects having C/C, C/T, and T/T genotypes, respectively. Furthermore, the triglyceride content of low density lipoprotein, intermediate density lipoprotein and HDL, and the cholesterol content of intermediate density lipoprotein were found to be associated with variation at LIPC position -514. However, there was no association of this polymorphism with coronary heart disease. These data suggest that the LIPC promoter variation is likely to be the basis for variation in HL activity, which underlies the variation in serum lipoprotein phenotypes in this sample.