- For methods of prolonging life that do not include actual rejuvenation, see life span.
Rejuvenation was a term referring to any process process which reversed biological aging. There were several documented natural, medical, and technological methods by which rejuvenation could be accidentally or purposely achieved.
After having their youth drained to restore the women of an inhabited planet, James T. Kirk, Spock, Leonard McCoy and Lieutenant Carver were restored by having the transporter re-assemble them using the record of their patterns from their initial beam down. (TAS: "The Lorelei Signal")
Metaphasic radiation was found to actually rejuvenate individuals exposed to it, and it was thought that it could be developed into a treatment that could double the life span of Federation citizens. (Star Trek: Insurrection)
Rao Vantika experimented with rejuvenation drugs. (DS9: "The Passenger")
The term "rejuvenation" was also occasionally used for the Changeling process of regeneration. (DS9: "The Alternate")
The natives of Cerberus II had a rejuvenating process which was complex, dangerous, and was usually not administered to outsiders. (TNG: "Too Short A Season")
Some species also had the natural ability to rejuvenate humanoids. The Companion was one example. (TOS: "Metamorphosis")
Additionally, the novelization of All Good Things... claimed that the anti-time eruption had rejuvenating properties.