A massive fire has ripped through the upper floors of the Royal Marsden Hospital in central London.
More than 100 firefighters are at the scene to tackle the flames.
All the patients and staff have been moved out of the building to make sure they stay safe.
The blaze started on Wednesday afternoon and is being treated as "very serious" by the London Fire Brigade.
Doctors and nurses helped to take patients and medical equipment to nearby hospitals like the Royal Brompton.
About 100 patients were moved to St Paul's Church, where they were cared for by nursing staff.
Back at the Royal Marsden, the roof has been almost completely destroyed in the fire, which sent smoke billowing across London.
The hospital was the first in the world to be dedicated to cancer treatment and research into the causes of the disease.