Police received a report of an avalanche in the Coire Leis area of Lochaber at about 1.10pm today.
The female hillwalker is said to be in a serious condition, Police Scotland said.
The Lochaber Mountain Rescue Team and a Royal Navy helicopter from HMS Gannet in Prestwick, Ayrshire, are at the scene.
Meanwhile, police rescued a fallen hillwalker in the Kinlochleven area.
Police received reports that the man had fallen approximately 20 to 30 metres whilst out walking in the area at around 3.30pm today.
The injured man, who was conscious and breathing, was flown to a waiting ambulance and subsequently taken to Belford Hospital.
Assistance has been provided by Glencoe Mountain Rescue Team and Royal Navy Rescue Helicopter 177.