A total of 10 patients were examined. In five children who suffered from secondary cardiomyopathy accompanying progressive muscular dystrophy scintigraphic examination of the myocardium was made using 99mTc-labelled pyrophosphate. In two cases the scan was distinctly positive, in three cases negative. Five men with poorly defined primary nonobstructive cardiomyopathy were examined too. The scan was positive in three cases and negative in two cases. The positivity of the pyrophosphate scan of the heart is therefore not pathonomonic of ischaemic damage. An increased accumulation of pyrophosphate in the myocardium in cardiomyopathy indicates an acute phase of the disease.