Subject to the assumptions of zero starting pressure, covolume equal to charge volume, burning rate proportional to pressure, constant burning surface, and no heat loss through gas or projectile friction, the equations of interior ballistics are presented in simple form. It is hoped that these simple equations will be of some aid in making ready approximate evaluations of the effect of variation of any parameter. The general equations are listed in section I. In section II the expressions for the maximum pressure and muzzle velocity are discussed more fully, and the derivatives with respect to various parameters are given.