A wheelchair has an adjustable seat that can be raised and lowered between a normal wheelchair operating height and ground level for enabling a wheelchair-dependent person to gain access to the seat from ground level and independently raise himself or herself from the ground level to the normal operating height. The seat can be further raised above the normal operating height to a higher level for improved reaching capability. In one embodiment, an elongate shaft is connected to the seat for rotation about its longitudinal axis. A plurality of cables have first ends that are connected to a wheelchair supporting frame and second ends that are connected to the elongate shaft. Rotation of the shaft about its longitudinal axis in one direction causes the cables to wind around the shaft to thereby raise the seat. Rotation of the shaft in the opposite direction causes the cables to unwind from the shaft to thereby lower the seat. In a further embodiment, the wheelchair supporting frame includes a lower frame portion and an upper frame portion that is adjustable in height with respect to the lower frame portion.