Cell therapy is a type of organ transplant which involves the transplant of human or animal cells to replace or repair damaged tissue and/or cells. The theory behind cell therapy holds that the best way to treat an illness is to use living tissue to restore the ailing. The procedure entails injecting either whole fetal animal cells or cell extracts from human tissue (of the patient or a third person) into the patient. Supporters of this form of therapy believe that embryonic and fetal animal tissue contain active therapeutic agents which induce healing. Based on the theory of like cures like, the types of cells used correspond in some way with the organ or tissue being treated.

Cells to be used may be prepared by extracting them from the patient and culturing them until they multiply to the level needed for transplant. In another procedure, fetal tissue that has just been removed from an animal is prepared and either injected immediately into the patient or freeze-dried before being injected. Cell therapy has been used to treat a wide range of conditions such as arteriosclerosis, as well as to rebuild damaged cartilage in joints, strengthen a weakened immune system, and help patients with neurological disorders. However, as many forms of cell therapy are still in their experimental stages, patients should be careful when approaching these treatments.