Radionics—also called electromagnetic therapy (EMT) and the Abrams method—is a form of alternative medicine that claims that disease can be diagnosed and treated by applying electromagnetic radiation (EMR), such as radio waves, to the body from an electrically powered device. It is similar to magnet therapy, which also applies EMR to the body but uses a magnet that generates a static electromagnetic field.

The concept behind radionics originated with two books published by American physician Albert Abrams in 1909 and 1910. Over the next decade, Abrams became a millionaire by leasing EMT machines, which he designed himself. This so-called treatment contradicts the principles of physics and biology and therefore is widely considered pseudoscientific. The United States Food and Drug Administration does not recognize any legitimate medical use for radionic devices.

Several systematic reviews have shown radionics is no more effective than placebo and falls into the category of pseudoscience.

Beginning around 1909, Albert Abrams (1864–1924) began to claim that he could detect "energy frequencies" in his patients' bodies. The idea was that a healthy person will have certain energy frequencies moving through their body that define health, while an unhealthy person will exhibit other, different energy frequencies that define disorders. He said he could cure people by "balancing" their discordant frequencies and claimed that his devices are sensitive enough that he could tell someone's religion by looking at a drop of blood. He developed thirteen devices and became a millionaire leasing his devices, and the American Medical Association described him as the "dean of gadget quacks". His devices were definitively proven useless by an independent investigation commissioned by Scientific American in 1924. He used "frequency" not in its standard meaning, but to describe an imputed energy type, which does not correspond to any property of energy in the scientific sense.

In one form of radionics popularised by Abrams, some blood on a bit of filter paper is attached to a device Abrams called a "dynamizer", which is attached by wires to a string of other devices and then to the forehead of a healthy volunteer, facing west in a dim light. By tapping on his abdomen and searching for areas of "dullness", disease in the donor of the blood is diagnosed by proxy. Handwriting analysis is also used to diagnose disease under this scheme. Having done this, the practitioner may use a special device known as an oscilloclast or any of a range of other devices to broadcast vibrations at the patient in order to attempt to heal them.

Other notable quack devices in radionics have included the Ionaco and the Hieronymus machine.

Some people claim to have the paranormal or parapsychological ability to detect "radiation" within the human body, which they call radiesthesia. According to the theory, all human bodies give off unique or characteristic "radiations" as do all other physical bodies or objects. Such radiations are often termed an "aura". Radiesthesia is cited as the explanation of such phenomena as dowsing by rods and pendulums in order to locate buried substances, diagnose illnesses, and the like. Radiesthesia has been described as a mixture of occultism and pseudoscience by critics.

Modern practitioners conceptualize these devices merely as a focusing aid to the practitioner's proclaimed dowsing abilities, and claim that there is no longer any need for the device to have any demonstrable function. Indeed, Abrams's black boxes had no purpose of their own, being merely obfuscated collections of wires and electronic parts.