It has long been known that beta-receptor blocking agents, including mainly cardioselective compounds, have favourable effects on tachyarrhythmias of various origins. They are the only substances known so far in the post-infarction phase to reduce significantly sudden cardiac deaths and to lower the rate of recurrent infarctions. High-risk patients seem to benefit most from the application of cardioselective beta blockers. In the acute infarction phase as well, beta-receptor blockers display favourable effects in the majority of patients, especially as they reduce the myocardial-infarct size and lower the tendency to arrhythmias by protecting the heart from sympathetic stimulation. The favourable effect on the variability of the heart rate must be stressed. Furthermore, the early application of beta-receptor blockers is recommended today not only in the event of hyperkinetic reactivity, but also and particularly in so-called high-risk patients, although always respecting the contra-indication. In these patients, mortality is reduced markedly in the long-term treatment.