Rob Lowe recalled the moment he was "completely" knocked out by "Outsiders" co-star Tom Cruise.

Lowe and Cruise first met in 1980 when they were just teens and the "Mission: Impossible" star was living with Emilio Estevez. The 18-year-old actor had just finished filming "Taps," according to Lowe.

The "Wayne's World" star explained he has a lot of "favorite" Cruise moments, but the one from the set of "The Outsiders" has always stuck with him.

"He’s so competitive that we used to box in the hallway of the hotel we were staying at during ‘Outsiders,’" Lowe said during an episode of the "The Rich Eisen Show." "So much testosterone. We’re 18-year-old guys stuck on location. So we would wear headgear, and we’d have mouthpieces in, but we would legitimately spar."

‘THE OUTSIDERS’ STARS TOM CRUISE, ROB LOWE, RALPH MACCHIO SEEN IN NEWLY RELEASED AUDITION FOOTAGE

A photo of Rob Lowe and Tom Cruise in 1980 next to a photo of Rob Lowe

Rob Lowe recalled being "completely" knocked out by Tom Cruise when they were teens. (Getty Images)

Rob Lowe in 1980

Rob Lowe photographed in 1980. (Getty Images)

In one particular boxing match, Cruise "completely" knocked out Lowe.

"And I just remember, Tom was jacked, and I had pipe cleaner arms," the actor recalled.

"But I hit him real clean, and I rang his bell, and the next I knew, I woke up – I was coming to, on the floor," Lowe added. "And he, like, completely knocked me out."

"His eyes just went black, but that’s the stuff we did. That’s what guys do. It's like ‘Fight Club.’"

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Cast of "The Outsiders"

"The Outsiders" starred Patrick Swayze, Matt Dillon, Rob Lowe, Emilio Estevez, Ralph Macchio, Thomas C. Howell, and Tom Cruise, and was directed by Francis Ford Coppola. (Sunset Boulevard/Corbis)

"The Outsiders" starred Lowe and Cruise along with Matt Dillon, Patrick Swayze, Ralph Macchio and Diane Lane. Francis Ford Coppola, the movie's director, shared footage from the film's audition process in March.

"42 years ago we cast ‘The Outsiders’ in a unique way," he wrote on Instagram.

"We had all the actors together on a soundstage and would alternate different actors reading for different roles," he continued. "It was interesting because each of them was watching their competition, so while it could’ve been a volatile situation, it turned into a very positive one."

"There emerged the natural respect and sense of colleagueship among them. The result worked beautifully and reminded me of my days as a camp counselor."

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The Outsiders cast

Tom Cruise and Rob Lowe would box at the hotel they stayed at while filming "The Outsiders." ( Sunset Boulevard/Corbis via Getty Images)

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The cast commented on the post, thanking Coppola.

"These auditions and this film experience still inform me today. Thank you, Francis (and Susie)," Macchio wrote.

"Feels like this was just yesterday!" Lowe explained. The actor previously spoke about his experience filming "The Outsiders" with Fox News Digital.

"It was my first time away from home, it was my first movie. I'll never forget it," he said. "It feels like it was four days ago, not 40 years."

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