Blood, serum and urine (24-hour-samples) concentrations of cadmium, zinc, calcium and magnesium were determined by means of atomic absorption spectrophotometry in 60 patients, therefrom 30 patients with idiopathic dilated cardiomyopathy (IDC) and 30 patients with coronary heart disease (CHD). The data of heavy metal and trace element concentrations of IDC and CHD patients were compared with each other and furthermore, for each group separately, correlated with patients history data, laboratory evaluations and data from heart catherization protocol. IDC patients showed higher blood cadmium concentrations (p less than 0.001) and lower serum zinc concentrations (p less than 0.001) compared to CHD patients. Serum levels of calcium and magnesium were not different in both groups. In urine samples IDC patients had lower concentrations of calcium (p less than 0.01) and magnesium (p less than 0.01) compared to CHD patients. Urine concentrations of cadmium and zinc were in the same range in both groups. The comparison of heavy metal and trace element concentrations with clinical data did not reveal definite correlations, however, data from experimental studies pointing out interactions of heavy metals and trace elements, could serve as useful interpretations. Hypomagnesemia in both patient groups (IDC, CHD) requires clinical follow up and substitution treatment.