By Stephen Gibbs
BBC News, Havana
Cuban President Fidel Castro has portrayed as wishful thinking reports from the United States that he is suffering from Parkinson's Disease.
Castro made his point during a trademark marathon speech
In a speech lasting over five hours, he said he felt fine and remarked that his ideological enemies had declared him dead on several previous occasions.
On Wednesday, a Miami newspaper said the CIA recently concluded that Mr Castro is showing signs of Parkinson's.
CIA experts made the diagnosis after analysing his public appearances.
In front of a group of Havana University students, Fidel Castro, looking fit and in good spirits, mocked the latest reports that he is suffering from a debilitating illness.
He said he had never felt better and although he did not issue an outright denial that he had Parkinson's disease, the fact that he stood and delivered a wide-ranging speech for several hours appeared to be designed to make a point.
The president's health has been the subject of speculation for much of his 46 years in power.
He is now 79 and his occasional brief lapses in concentration during speeches do heighten the speculation.
But Cuban officials say that those close to the veteran leader can only marvel at his stamina - and Fidel Castro himself says that anyone who hopes that the Cuban revolution will come to an end when he dies will be proved wrong.