Abstract: A brake system for a wheelchair comprises a base plate fixed to a frame of the wheelchair and a swing lever pivotally mounted to the base plate and provided with a brake member engagable with a circumferential surface of a wheel of the wheelchair. A toggle joint mechanism composed of two pivotally interconnected links is pivotally mounted to the base plate and connected to the swing lever to move the swing lever between an extended braking position and a retracted inoperative position. An operating lever is pivotally mounted to the pivot which interconnects the two links of the toggle joint mechanism. The operating lever has cam surfaces engageable with the two links to depress the latter when the operating lever is moved in either of two directions by pushing it or pulling it. Such action drives the swing lever into braking engagement with the wheel. A biasing spring is provided to urge the links of the toggle mechanism towards retracted position.