Conventional (steel-like) material helical gears can be replaced by helical gears made of composite materials. This results in light-weight helical gears, which add to the existing list of advantages of helical gears, such as smooth and silent operation and larger load carrying capacity, while at the same time maintaining higher strengths, which is an important requirement in applications like spacecraft and aircraft. In the present work, the performance of Kevlar/epoxy and graphite/epoxy material helical gears has been compared with that of carbon steel helical gears using a three-dimensional finite element method. From the present it may be concluded that composite material helical gears behave similarly to carbon steel helical gears and graphite/epoxy helical gear behaviour is very close to that of carbon steel helical gears, except for the slightly larger displacements at the tip. The safety factor obtained based on the root stress values for the two orthotropic material helical gears is very favourable. © 1993.