Edward Kennedy, a prominent US Democratic senator, is now "conscious, talking, joking with family", after being rushed to a hospital in Massachusetts after suffering a seizure, his spokeswoman said.
Stephanie Cutter said on Saturday he was undergoing tests at Massachusetts General Hospital to determine the cause of the seizure.
Kennedy's wife, Victoria, two of his children and niece Caroline Kennedy were among those with him at the hospital.
An official who declined to be identified by name, had earlier said that Kennedy had stroke-like symptoms. The hospital declined to comment on his condition.
Kennedy, 76, is the last surviving brother of former president John F Kennedy, who was assassinated on November 22, 1963.
His brother Robert Kennedy was assassinated on June 5, 1968, as he was campaigning for the presidency.
A fierce critic of George Bush, the current US president, Kennedy is a supporter of Barack Obama, who is running for the Democratic nomination to contest a presidential election in November.
First elected to the senate in 1962, he is the second longest-serving senator after Robert Byrd of West Virginia.