Josh Hartnett has been admitted to a Los Angeles hospital with gastrointestinal problems, his publicist has said.
The 30-year-old was taken to Cedars-Sinai Medical Center by ambulance at 0145 local time on Monday morning.
Susan Patricola said in a statement the star was "under observation but is resting comfortably".
Hartnett made his West End debut in a stage adaptation of the Oscar-winning film Rain Man last year.
Source: Press Release