Oil tycoon T. Boone Pickens is recovering after suffering a mini-stroke last month.
Jay Rosser, Pickens' chief of staff, said in an email Monday the mini-stroke happened a few days before Christmas and Pickens was hospitalized for a few days.
In a tweet he sent out on Monday, the 88-year-old Pickens said that this will be "another 'Old Man Makes a Comeback' story."
Rosser says Pickens' speech was affected by the mini-stroke, but not severely, and he is undergoing daily speech therapy.
Pickens said in his tweet he was back working at his Dallas-based investment firm BP Capital.
Rosser said that Pickens, who made his fortune as a Texas oil producer but has also championed alternative energy forms, worked all last week and was back in the office this week.