Emergency personnel received a report of an injury near the Rock City area of Mount Diablo at 8:41 p.m. and found the victim 70 feet down a ravine with a broken leg.
Fire crews were able to pull the man up from his landing point with a rescue basket, according to San Ramon Valley fire Battalion Chief John Viera.
The man was then flown to John Muir Medical Center in Walnut Creek.
Steep terrain, darkness and poison oak plants in the area created hazardous conditions for the emergency personnel, Viera said.
