The immediate and medium term (3 years) of unstable angors was specified by the study of 100 hospitalized patients. The cases selection was based on the existence of angina pain which had appeared or reappeared less than a month before, during more than fifteen minutes and/or repeated, which were more and more frequent, less and less sensitive to nitroglycerine, and in the absence of recent myocardial infarction signs. The immediate course seemed relatively favorable; during the initial hospitalisation there were only nine myocardial infarctions and three deaths. The alarming factors of initial prognosis are essentially the persistence or recurrence under medical treatment of angina pain hardly relieved by nitroglycerine. The course over three years was bad; 23.6% of deaths, especially of cardiac origin (14/17) were noted; more than 80% or the surviving patients kept enduring more or less severe pains; persistence of electric signs on the ECG during the initial course was the only significant pronostic factor that was regularly noted. As regards the 16 patients treated by surgery, operative death rate remained high (3/16), but remote functional results were good (8/12 asymptomatic). Only randomized studies on homogenous groups, carried out during an enough long course, will enable us to specify therapeutic indications better.