Abstract: A wheelchair lift system enabling wheelchair accessibility between stair levels for persons incapable of traversing stairs under their own power. The key of the invention is a free-rolling, wheeled platform suspended between two arcuate tracks which are lifted and lowered by synchronized, reversible, worm-gear drive mechanisms. The platform and tracks are mounted on a frame in which also resides peripheral equipment needed to raise and lower the system. A seven-foot-high portal frame supports the drive mechanism which comprises pivoting, worm-gear type drive motors, turning long worm-gears extending vertically downward from the top of the frame to the floor and engaging pivoting worm-gear heads that are attached to the arcuate tracks, while allowing normal access to the stairs.