The article presents design concepts that will accurately model the stresses in internal gears. The article employs a finite element method to investigate the effects of different parameters on the stresses of the gear. A simulation of the stress fluctuations when two gears mesh is presented. The areas examined are: effects of rim thickness and fillet radius on the root fillet stress; effects of loading position; effects of support condition; effects of different pressure angles on the root fillet stresses.