Chemical means of enhanced interrogation used by agents on both sides.
- Maxwell Smart slips a newly developed instant truth serum into the drink of KAOS agent Mary "Jack" Armstrong. However, Armstrong is able to switch her drink with Max's and Max ends up revealing his identity and mission to her [Episode #15: "Survival of the Fattest"].
- In a similar incident the following year, Max drops truth serum in pill form into the drink of KAOS agent Lisa Smith. Once again, the drinks are switched and in a subsequent conversation with the Chief Max gives the latter a brutally honest appraisal of his running of CONTROL, adding that he is "not the smartest man in the world" [Episode #49: "The Mummy"].
- After Max deliberately allows himself to be captured, KAOS agent Kimmel orders that he be injected with a new truth serum developed by scientist Seidlitz designed to force him to reveal any memorized information. However, since he is acting as a decoy to protect another agent on the real mission, Max has no secret information to reveal and instead begins to recite multiplication tables and rhymes learned when he was child [Episode #37: "The Decoy"].
- A variant on truth serum is the truth steam administered by KAOS agent Montague Leach at his chain of spas called Roman Baths. When Max and the Chief are unwittingly exposed to the steam they reveal how they truly feel about each other [Episode #134: "Smartacus"].