The diet-heart hypothesis proposes that elevated intakes of total fat, saturated fat, and dietary cholesterol raise serum cholesterol, which in turn increases the risk of developing coronary heart disease (CHD). To examine the relationship between dietary intake and 12-year CHD mortality we used data from the Lipid Research Clinics Prevalence Follow-Up Study. Dietary intake was measured at study entry using the 24-hour recall technique among 4546 North American men and women who were at least 30 years old and initially free of CHD. Proportional hazards analyses controlling for total energy intake indicated that increasing percentages of energy intake as total fat (RR 1.04, 95% CI = 1.01-1.08), saturated fat (RR 1.11, CI = 1.04-1.18), and monounsaturated fat (RR 1.08, CI = 1.01-1.16) were significant risk factors for CHD mortality among 30 to 59 year olds. The increasing percentage of energy intake from carbohydrate had a significant protective effect (RR 0.96, CI = 0.94-0.99). The strength of these associations was not diminished after adjustment for specific serum lipids, suggesting that serum lipids did not mediate the effect of diet on CHD mortality. None of the dietary components were significantly associated with CHD mortality among those aged 60-79 years. We conclude that future research must be directed toward better understanding the pathway between dietary intake and coronary disease as the current diet-lipid-heart hypothesis may be overly simplistic.