This study analyzes the forming principle of spur gears with asymmetric teeth profile by rack-type and pinion-type cutters. Mathematical models of generating and generated surfaces manufactured by generating-type cutters are given. Asymmetric gear tooth is also considered. A computer program is developed to display computer graphs of the spur gears with asymmetric involute teeth. The simulated motion path of the generating cutter is illustrated. The developed computer programs are very helpful in the design of involute gears.