Canadian Forces Base Trenton says the man lost his footing and fell an unknown distance while hiking Thursday near Montreal River, about 65 kilometres north of Sault Ste. Marie, Ont.
The base says search and rescue technicians tried to extricate him during the evening, but could not do so because of the dark.
A base official says the rescuers stayed with the man and provided medical care until more technicians, a plane and a helicopter arrived at about 7:30 a.m. Friday.
There is no immediate word on the man's condition.