Along with the beneficial effects of beta blockers in the ischemic derangements of myocardial energy metabolism are nonspecific membrane effects, which are thought to derive from the physicochemical interaction of the drugs with the cell membrane. These interactions are observed in various forms (e.g., membrane stabilizing action, quinidine-like action, cardiodepressant action), depending on the intensity of the interaction and on the method used for their detection. There may be still other manifestations that have not been detected so far, owing to our ignorance of their existence and our lack of an adequate method for their detection. The importance of the presence of specific chemical moieties in certain beta blockers with ability to trap peroxy radicals is also discussed.