At one moment, Israel set up an informal committee to advise on the state of Mr Arafat's health. It decided he did not have Parkinson's disease, though he does have many of the symptoms, such as shaking limbs and lips and fixed eyes.
His closest aides are protective. They say many of the signs of his deteriorating health are the consequence of his plane crash in Libya on 7 April 1992.
Several months after the crash doctors in Jordan removed a blood clot in his brain, an apparent result of the crash landing.
Mr Arafat is 69 and works famously hard, particularly at night. Few decisions in the Palestinian Authority, which runs Gaza and the Palestinian enclaves on the West Bank, are reached without him.
But since Benjamin Netanyahu was elected Israeli prime minister in 1996 the Palestinian leader has been depressed - his depression sometimes coming close to a nervous breakdown.
He speaks less in English than he used to, and his aides seem to coach him more.
But there are few signs that Mr Arafat's memory is fading. He is as deft as ever in manoeuvring within Palestinian politics as was demonstrated during the latest crisis in relations with the Islamic militant group Hamas. His political problems have more to do with Mr Netanyahu's intransigence. The Israeli leader is prepared to talk at almost any length about the Oslo accord, but not to implement it.
Nevertheless, the Palestinian leader is sticking to his strategy of trying to cultivate American, European and Arab support in order to put pressure on Israel. He has steered away from suggestions that the Palestinians need to prove on the streets that they will not accept the present status quo.
If Mr Arafat dies, Abu Mazen, who negotiated so much of the Oslo agreement, is his most obvious successor. But whoever takes over will depend on the Palestinian security services.
He will also lack Mr Arafat's popular appeal among the 6 million Palestinians in the world and his reputation as an old revolutionary, as well as a diplomat.Reuse content