This paper studies the computerized tooth profile generation of involute helical gears cut by rack cutters with asymmetric teeth. The asymmetry means that different pressure angles are applied for driving and coast sides, respectively. Based on the theory of gearing and the geometry of straight-sided rack cutter, a complete mathematical model of asymmetric helical gears including working region, root fillet and bottomland is given. Undercutting analysis is also investigated by considering the relative velocity and equation of meshing. A computer program is developed to generate the tooth profile of helical gears with asymmetric involute teeth.