In this paper, the authors present methods for designing of non-circular gears, including internal and external gears with spur or helical teeth. Technology related issues that determine tooth profile calculation algorithm are described. The results presented in this paper can become groundwork for further investigations of other particular properties of non-circular gears, similar to investigations of spur, helical and bevel gears. Examples of such properties include kinematics and application of special purpose gears or issues related to strength, dynamics, tribology, etc.