Black contributed to basic scientific and clinical knowledge in cardiology, both as a physician and as a basic scientist. His invention of propranolol, the beta adrenergic receptor antagonist that revolutionised the medical management of angina pectoris, is considered to be one of the most important contributions to clinical medicine and pharmacology of the 20th century. Propranolol has been described as the greatest breakthrough in heart disease treatments since the 18th century discovery of digitalis and has benefited millions of people. Black's method of research, his discoveries about adrenergic pharmacology, and his clarification of the mechanisms of cardiac action are all strengths of his work.