Ben Stiller and Reese Witherspoon have signed on to star in an untitled Cameron Crowe comedy for Columbia Pictures, according to Variety.

At this stage we don’t know anything about the project, except that it’s a mix between comedy and adventure. Plot details are still kept under wraps.

Cameron Crowe wrote the script and will also produce and direct. His last film, “Elizabethtown,” was released in 2005. His credits also include “Almost Famous” and “Vanilla Sky.”

The film will not start principal photography until January 2009.

Stiller recently starred in “The Heartbreak Kid” and will next be seen in the action comedy “Tropic Thunder,” which he also directed. He’s currently filming “Night at the Museum 2: Escape from the Smithsonian.”

Witherspoon recently appeared in “Rendition” and will next be seen in Seth Gordon’s comedy “Four Christmases.” She’s currently working on DreamWorks Animation’s “Monsters vs. Aliens.”