Making his first public appearance Sunday in the nine months since his stroke, the 53-year-old Kirk walked the stairs from the 66th floor to the 103rd floor of the building now known as Willis Tower, the Chicago Tribune reported.
The event, called Skyrise Chicago, raised money for the Rehabilitation Institute of Chicago, where Kirk is undergoing therapy.
"I'm here. Where's the beer?" Kirk declared after he climbed the stairs wearing a brace on his left leg and holding the hand rail.
His activities were monitored by a physical therapist from the center.
The senator has undergone three brain surgeries.
His aides have declined to say when he might return to work. Kirk was elected to the Senate two years ago.