Existing jet mixing theory is reviewed and compared with available experimental results. Simple mixing equations are developed and used to determine the total pressure variation in a two-dimensional jet and the effect of a static pressure change on momentum flux. The effects of free-air entrainment are studied and potential flow solutions given for three particular cases. A method of calculating the lift loss due to vortices arising from viscous mixing is derived and gives good agreement with experiment. The effect of jet mixing on cushion pressure is investigated, using two approaches. The mixing equations are used to estimate total head loss in a recirculating jet and found to agree with experiment. The report concludes with some experimental observations of the static pressure distribution near a complex two-dimensional nozzle. (Author).