His spokesman says he is being treated for something "serious.""He had experienced some chest pains and he's in for testing," Gordon said.
The spokesman, Dick Gordon, said Yastrzemski went to Massachusetts General Hospital in the morning.
When asked if it was serious, Gordon said: "Any time you are in the hospital, it's got to be pretty serious."
The 68-year-old Yastrzemski was baseball's last player to win the Triple Crown in 1967 and was elected to the Hall of Fame in 1989.