A walker which can be used on stairs as well as on a level surface. The walker has legs which are comprised of hydraulic cylinders with integral pistons. Each pair of legs is part of a frame. The walker is configured such that each frame provides that fluid can flow from one leg of the frame to the other. Because the fluid is generally incompressible and the amount of fluid in each frame is fixed, movement of one piston of the frame causes the other piston of the frame to move. As such, as one leg of the frame lengthens, the other leg of the frame automatically shortens in response, and vise versa. While the walker is configured such that the legs can be shortened and lengthened, preferably the walker is also configured such that the legs can be locked in place.
