By introducing experimentally-obtained apparent mass components into the relevant equations of motion, performance characteristics of descending parachutes have been obtained which so resemble those observed as to give an appropriate basis for performance prediction. The effects on pitching oscillations caused by certain changes in system physical parameters; the size of the parachute canopy, the length of the rigging lines and the store mass, have all been considered as well as the effect of parachute altitude. For good stability in pitch the significant ratio of physical parameters is that of store mass to effective canopy mass, inclusive of apparent mass.