The clinical syndrome "coronary insufficiency with normal coronary arteriogram" is found in approximately 10% to 20% of patients with exercise-induced coronary insufficiency. In most of these cases, disturbances of the coronary microcirculation are present. They can appear in vascular diseases (arterial hypertension, systemic immunopathies, immune complex vasculitis), in rheologic diseases (paraproteinemia, hyperlipoproteinemia, polyglobulia) and in disturbances of transport and diffusion of oxygen (carbon monoxide intoxication, methemoglobinemia). The clinical diagnosis is based on the usual diagnostic procedures (electrocardiogram, exercise electrocardiogram, responsiveness to nitroglycerin), as well as on newer functionally oriented diagnostic procedures (determinations of coronary blood flow and coronary vascular reserve, production of lactate, serologic findings, histology and immune histology of peripheral arteries, measurements of viscosities in both plasma and blood). Many clinically relevant disturbances in the coronary microcirculation can thus be detected and treated on a rational basis by management of the underlying main disease, that is, by treatment of the vascular, rheologic and metabolic disorders. Persistent angina pectoris in the presence of a normal coronary arteriogram does not represent an end to coronary diagnostic procedures, but introduces the clinical task of using all diagnostic possibilities to enable functional and therapeutic assessment of the coronary microcirculation.