BACKGROUND The serum ratio of heart-type fatty acid-binding protein to myoglobin (F/M) has been shown to be a new marker for cardiac damage and volume overload in hemodialysis patients. We evaluated the utility of F/M in hemodialysis patients compared to control subjects. METHODS AND RESULTS Twenty-one hemodialysis patients and 17 control subjects with normal renal function were investigated. Using a cutoff point of mean + 2SD of the F/M in the controls (value: 0.147), the hemodialysis patients were divided into 2 groups. The concentrations of atrial natriuretic peptide (ANP) and brain natriuretic peptide after hemodialysis in the high F/M group were higher than those in the low F/M group. The mean level of ANP in the low F/M group was almost the upper limit of normal range. The values of left ventricular end-diastolic dimension and left ventricular mass index in the high F/M group were higher than those in the low F/M group, and the mean levels of those in the low F/M group were almost the same as those in the controls. CONCLUSIONS The F/M can be evaluated by the absolute value regardless of renal dysfunction, and the value of 0.147 might be useful for determining the cutoff level of cardiac involvement.