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BACKGROUND: In clinical practice, high triglyceride level is recognized as an indicator of increased risk of coronary heart disease (CHD), while most epidemiological studies have shown that triglyceride level is not an independent risk factor for CHD. In an effort to explain this discrepancy we reanalyzed the Helsinki Heart Study data in the light of findings from recent clinical studies related to the insulin resistance syndrome. METHODS: The log-linear modeling technique was used to study the pattern of cross-sectional interdependence of triglyceride level, high-density lipoprotein cholesterol (HDL-C) level, low-density lipoprotein cholesterol level, blood pressure, and blood glucose level. The CHD risk associated with different combinations of levels of triglycerides, HDL-C, and blood pressure was assessed via Cox proportional hazards models. RESULTS: Triglycerides occupied a central role in the pattern of associations of the factors studied; in particular, the associations with HDL-C level, blood pressure, and blood glucose level were without threshold values. The prevalence of high triglyceride level plus low HDL-C level was strongly associated with blood pressure and blood glucose level, while the prevalence of low HDL-C level alone was not. Only the subgroup with both high triglyceride and low HDL-C levels showed a substantial CHD risk, while those with low HDL-C levels alone or high triglyceride levels alone showed a marginal risk. CONCLUSIONS: Our results suggest that triglycerides play a central mediating role in the occurrence of several CHD risk factors, especially those related to the insulin resistance syndrome. Because of these interdependencies, the question of an independent effect of triglycerides is not relevant, and when assessing CHD risk, triglycerides should be considered jointly with HDL-C.