 Coronary heart disease CHD is a complex disorder constituting a major health problem in Western societies. The study assesses the unknown genetic background of CHD by investigating the most common familial dyslipidemia predisposing to CHD, familial combined hyperlipidemia FCHL. The population prevalence of FCHL is estimated to be 1-2 percent and the disorder affects 10-20 percent of families with premature CHD. In FCHL, serum cholesterol, triglycerides, or both are elevated. Both environmental and genetic factors are suggested to affect the complex FCHL phenotype. Since the molecular basis of FCHL is unknown, a significant number of genetically predisposed individuals remain unidentified and exposed to premature CHD. The study uses samples from the genetically isolated population of Finland. 