Project T.A.H.I.T.I. was a high-level S.H.I.E.L.D. program, created for the purpose of saving a mortally wounded Avenger. Agent Phil Coulson was assigned to the project as its director. TAHITI began experiments with a drug milked from the corpse of a blue-skinned alien, codenamed the Guest Host, which prompted cellular regeneration in test subjects. Six S.H.I.E.L.D. agents with life-threatening illnesses such as cancer were selected. At first, the patients showed no ill side effects and Coulson was going to recommend them for immediate release. But the experiments were met with complications, as the test subjects began to suffer mental deterioration, ranging from hypergraphia, aphasia to complete psychosis, compelled to write out mysterious alien glyphs in any way they could. The project was unsure whether this was a side effect from the GH drugs or awareness of the experimentation. Doctor Goodman theorized that the Host's genetic memory was imprinting on the test subjects, creating a psychic schism. Coulson was all for terminating the project and destroying the Host, but Goodman argued for its value. The project attempted to mitigate these effects by re-writing memories, with barely consistent results. In the end, Coulson resigned as project director and recommended to Director Fury that the project be shut down and never used on anyone. 
After the Battle of New York, Fury reactivated Project T.A.H.I.T.I. to revive Coulson, who had died at Loki's hands. He brought in physicians such as Doctor Streiten and Doctor Goodman and numerous operations were performed to restore Coulson to life. However, the neurological damage was extensive, as Coulson repeatedly begged to die, but the doctors instead cut open his head and applied a memory probe to rewrite his memories, make him assume he had taken a trip to Tahiti.
- 8 Project T.A.H.I.T.I. (Earth-199999) Members
- 3 Appearances of Project T.A.H.I.T.I. (Earth-199999)
- Minor Appearances of Project T.A.H.I.T.I. (Earth-199999)
- 7 Media Project T.A.H.I.T.I. (Earth-199999) was Mentioned in
- Images that include Project T.A.H.I.T.I. (Earth-199999)
- Team Gallery: Project T.A.H.I.T.I. (Earth-199999)