Publisher Summary The bioelectric processes in the heart, brain, and skeletal muscles have long been recorded, not only as methods of physiological research but also in connection with the great diagnostic possibilities for electrocardiography, electroencephalography, and electromyography. Along these basic directions of clinical electrophysiology, a great deal of factual material has accumulated indicating a connection between bioelectric phenomena and certain changes in the functional state of both individual cell structures and whole organs and systems. The experience gained in the long development of electrophysiology made it possible during the last two decades to enter a new phase in the practical utilization of its achievements. Now, work in the area of biocontrol is being done in dozens of laboratories in the USA, Canada, England, France, Italy, Poland, and Yugoslavia. The chapter presents the basic experiments. A substantial number of the devices developed for biocontrol can be classified according to the characteristics of the control signal into devices that control the biopotentials of the skeletal muscles, heart, and brain. The chapter discusses research in the area comprising the first two groups.