A survey is presented of research results of pyrophosphate myocardial scanning in 130 dogs and 150 patients with various myocardial lesions. The results of experiments in animals were immediately applied in clinical practice. The results showed that acute transmural myocardial lesions yielded practically in all instances positive scintigraphic findings. The findings in nontransmural infarctions were less convincing--they were positive in 60% of cases. Positive scintigraphic findings were also obtained in 80% of dogs with experimentally induced temporary ischaemia, and in 80% of dogs with experimentally induced dystrophy of the myocardium. In patients with angina pectoris positive findings were obtained in 1/3 of the cases, and in patients with cardiomyopathies, in 1/3 to 1/4 of the cases (in dependence on the etiology of the cardiomyopathy). It appears that 99mTc-PYP is a highly sensitive, but nonspecific, detector of myocardial lesions.