In order to clarify the basic mechanism(s) linking radiation exposure and coronary heart disease (CHD), we here collected ultrasonographic data on fatty liver and measured levels of metabolic CHD risk factors from November 1990 through October 1992 in 1,517 Nagasaki atomic bomb survivors (575 men and 942 women). Using a cross-sectional study design, we examined the effects of radiation dose on fatty liver and CHD risk factors by means of a multiple logistic regression model. Fatty liver was related to the metabolic CHD risk factors associated with insulin resistance syndrome: obesity, hypertension, hypercholesterolemia, low high density lipoprotein (HDL)-cholesterol, hypertriglyceridemia, and abnormal glucose metabolism. Radiation dose was positively related to fatty liver, low HDL-cholesterol, and hypertriglyceridemia, whereas it had no effects on obesity, hypertension, hypercholesterolemia, or abnormal glucose metabolism. The present results suggested that radiation dose was related to 1) fatty liver, which clustered the metabolic CHD risk factors associated with insulin resistance syndrome and 2) atherogenic lipid profiles. It is suggested that these associations are involved in the basic mechanism(s) linking radiation exposure and CHD.