Physicist Stephen Hawking should make a "full recovery" after being taken to hospital by ambulance, his employers said.
The 67-year-old, who is based at Cambridge University, was admitted to Addenbrooke's Hospital in Cambridge on Monday after being taken ill.
"Professor Hawking remains in hospital," said a university spokesman said.
"But he is in a comfortable condition and is expected to make a full recovery."
The university described Prof Hawking as being "very ill" when he was taken to hospital.
He is thought to be suffering from a respiratory infection.
The scientist suffers from Motor Neurone Disease, uses a wheelchair and speaks with the aid of a voice synthesiser.
He developed the disease while studying in the 1960s and is one of the longest surviving sufferers.
Prof Hawking is one of the world's leading cosmologists and has been based in Cambridge for more than 30 years.
He is the university's Lucasian Professor of Mathematics and is best known for his book A Brief History Of Time.
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