The clinical syndrome "coronary insufficiency at normal coronary arteriogram" is found in approximately 10-20 per cent of patients with exercise-induced coronary insufficiency. In most of these cases disturbances of coronary microcirculation are present. They can appear in vascular diseases (arterial hypertension, systemic immunopathies, immune complex vasculitis etc.), in rheological diseases (paraproteinemia, hyperlipoproteinemia, polyglobulia etc.) and in disturbances of transport and diffusion of oxygen (carbon monoxide intoxication, methemoglobinemia, hyperlipoproteinemia). The clinical diagnosis is based on usual diagnostic programs (electrocardiogram, exercise electrocardiogram, responsiveness to nitroglycerin etc.), as well as on a newer, functionally orientated diagnostic procedures (determinations of coronary blood flow and of coronary vascular reserve, production of lactate, serological findings, histology and immune histology of peripheral arteries, measurements of viscosities in both, plasma and blood etc.). Many clinically relevant disturbances in coronary microcirculation can thus be detected and therefore can be treated on a rational basis by the management of the internal main disease, this is by the treatment of the vascular, rheological and metabolic disorders. Persistent angina pectoris, in the presence of normal coronary arteriogram, represents no termination of coronary diagnostics, but moreover implies the clinical task for using newer diagnostic possibilities in order to enable functional and therapeutical assessment of coronary microcirculation.