More than 100 patients had to be evacuated from Aberdeen Royal Infirmary after a fire broke out in one of the wards.
The fire started in ward 34, on the second floor of the main building of the hospital, at about 0200 BST.
The ward is used for patients recovering from surgery.
Fifty firefighters tackled the blaze which also affected nearby wards. An ARI spokeswoman said 109 patients were moved to other parts of the hospital.
Grampian Fire and Rescue Service said no-one was hurt but a large amount of smoke affected other wards.
Six fire appliances were called out from across Aberdeen.
The ARI spokeswoman said: "Patients from wards in the vicinity of ward 34 were also evacuated as a precaution. It's not brought the hospital to a complete halt. We are able to maintain our services."
Dr Pauline Strachan, chief operating officer for NHS Grampian, praised the actions of staff and firefighters.
"Our top priority has been, and remains, the safety of our patients and our staff and to maintain our hospital services, she said.
"Our senior nurses and managers co-ordinated the moving of patients.
"The response of staff has been excellent. Staff have worked very hard to ensure that patients are properly looked after, while being moved to and settled into other parts of the hospital."
Grampian Fire and Rescue Service have launched an investigation into the blaze.