Corporelectroscopy

Corporelectroscopy was the process by which two (or more) people switched their minds into each others' bodies. It could also allow one mind to take over another completely, enabling one brain to move into another individual's body, effectively taking control and killing the other.

The Javaman, a scientist with considerable imagination, called corporelectroscopy a "scientific implausibility". He was unaware that the theta-waves emitted by his Dorganator had caused the process to occur with the Sixth Doctor and Peri Brown. The Doctor later told Peri that corporelectroscopy was dangerous knowledge, and that it was "best left to the Time Lords". (PROSE: Turnabout is Fair Play)

Coporelectroscopy was used by Kroagnon to transplant his brain into the Chief Caretaker of Paradise Towers. This brought about physical changes in the Chief: he walked stiffly, spoke as though his tongue was swollen, his skin took on a silvery colour, and his moustache grew. (TV: Paradise Towers)

Similar processes
Crozier developed a method that allowed the Mentor Kiv to take over Peri's body, and would allow him to continue taking over bodies and become immortal. The High Council of the Time Lords manipulated Yrcanos as an assassin to stop Crozier and Kiv, as natural flow of evolution would've been upset. (TV: Mindwarp)

The banned psychograft allowed one mind to take over another body, with the former's body being destroyed. The overtaken mind would still exist but be slowly compressed to death. (TV: New Earth)