Martina Navratilova has been treated in hospital in Kenya with an accumulation of fluid in the lungs after attempting to climb Africa's highest peak.
The 54-year-old tennis great has been diagnosed with high-altitude pulmonary edema, said Dr David Silverstein, a consultant in cardiology and internal medicine at Nairobi Hospital.
"It is potentially dangerous when someone is at high altitude, but once brought down, recovery is quick," he said. "Martina is doing well and will continue to do well."
Navratilova had been assisted down Mount Kilimanjaro by porters and driven to the Kilimanjaro Christian Medical Centre for assessment after having to abandon her attempt to climb the mountain in Tanzania for a sport charity.
The 27-person climbing team Navratilova was part of has faced heavy snows and mist since beginning the climb up the 19,340-foot mountain on Monday.
"I'm disappointed not to be able to complete this amazing journey," she said in the statement. "It was something that I have wanted to do for so long but it was not to be."
Navratilova, who won 18 singles Grand Slams, said last weekend that she has never climbed higher than 12,000 feet. She had reached nearly 14,800 feet when she was forced to give up after feeling unwell, according to the charity.
The Aspen, Colorado resident said she was "petrified" of failing to reach the summit "because then the whole world will know".
Navratilova was climbing the mountain to raise money and awareness for the Laureus Sport for Good Foundation. The rest of the team will continue the climb and should reach the summit on Saturday.