A roof rail air bag assembly includes an air bag module having an air bag and an air bag inflator, and a hanger designed to attach the assembly to the roof rail of a vehicle. The installation of the roof rail air bag assembly is accomplished by an operator standing outside the vehicle, and without the use of external fasteners. A roof panel is attached to the vehicle roof rail to permanently fasten the hanger to the vehicle, while the air bag module can be easily removed for servicing.