Abstract: An automatic braking system for wheelchairs which prevents rearward, downhill motion of wheelchairs while having no effect on horizontal or uphill motion. The braking system is made up of circular ratcheted plates which are attached to the axles of the driving wheels of the wheelchair and L-shaped members slightly in front of and beneath the ratcheted. The L-shaped members are rotatable about axles located in their angles. The long leg of an L-shaped member is directed downwardly by gravity and maintains the short leg in a substantially horizontal position. The short leg forms a pawl which engages the ratchets of the plate when the wheels start to roll backwards when the wheelchair is directed upwardly, thus automatically stopping the wheelchair.