Former Australia captain and World Cup winner Michael Lynagh was in a stable condition on Thursday after suffering a stroke, rugby officials said.
The 48-year-old, regarded as one of rugby's all-time greats, was rushed to hospital complaining of headaches and blurred vision.
"Former Queensland Reds and Wallabies captain Michael Lynagh was hospitalised in Brisbane on Monday night after suffering a stroke," Queensland Rugby Union (QRU) said in a statement.
"Mr Lynagh remains in a stabilised condition in the Royal Brisbane Hospital and is undergoing tests in an effort to discover the cause of the illness."
Lynagh, who now lives in Britain, won 72 caps for Australia in the 1980s and 1990s as well as having a distinguished state career for Queensland.
He was part of Australia's Grand Slam winning team in 1984 and was a key player in the Wallabies' 1991 World Cup win.
Lynagh captained Australia from 1993 to 1995 and held the world points scoring record when he retired with 911 points. He also held the world record for most conversions (140).
He went on to play for Saracens in England and has had a successful career as a marketing director since his retirement from rugby.
Australian Rugby Union chief executive John O'Neill said his office had been inundated by enquiries from Australia and around the world requesting information on Lynagh's condition.
"It is an indication of the status he holds within our great game," he said.
"Michael has been a wonderful Wallaby, but also a wonderful man, which explains the outpourings of support and good luck messages to him."
Another former Australia captain, Andrew Slack, who wrote Lynagh's authorised biography, said he was shocked at his illness.
"There's not a lot known but he's stayed very fit since retiring some years ago," he told ABC radio.
"I think this is a bolt out of the blue, there's no doubt about that."© ANP/AFP