A computer program for calculating heat release rates from stratified-charge rotary engines is described. Important aspects of the program include calculation of equilibrium combustion product properties, treatment of both liquid and gas phase fuel in the chamber, heat transfer, leakage past side and apex seals, and crevice effects. Heat release rates are presented from 580 and 70 Series rotary engines. Combustion in the 580 Series engine exhibits two distinct phases. The first phase occurs rapidly, with a duration of approximately 40 shaft degrees. The second phase of combustion proceeds more slowly, with a duration of approximately 70 shaft degrees. Three phases of combustion are observed for the 70 Series engine. The third phase is attributed to burning of the pilot spray, and precedes the other two phases.