Since 1972 6 patients (4 males and 2 females) at the age from 18 to 44 years with myocardial infarctions could be observed whose coronary system in the subsequent coronarographic examinations proved to be unconspicuous. The diagnosis of the infarction was anamnestically, laboratory-chemically, electrocardiographically and partly scintigraphically ascertained. Issuing from features of infarction and pseudoinfarction, respectively, in the ECG other differential-diagnostically important cardiac and extracardiac causes could be excluded. In comparison to patients with coronary sclerosis typical symptomatology could not be delimited. Peculiarities of the clinical picture are the juvenile age, the in most cases short or lacking angina pectoris anamnesis, the frequent lack of factors of risk and the inclination to disturbances of rhythm. Up to now a satisfying etiologic clarification could not be rendered. The relevance of the different possibilities of the disturbed equilibrium between O2-offer and -need concerning the clinical course of our patients is discussed. Here on the side of the O2-offer the spasm of the big and small vessel and the disease of the small vessels are regarded as decisive factors of the development of the infarction, where as the coronary embolism with subsequent lysis is less to be taken into consideration. Other pathogenetic mechanisms, such as the pathologic Hb-O2-dissociation and the metabolic changes influencing the O2-need must be included into the causal chain of this presumably polyetiologic process. Prognostic and therapeutic aspects which closely correlate with the etiologic explanation are discussed.