Results of a theoretical investigation on the effect of the two-dimensional nonuniformity of air flow through the evaporator of automobile air conditioning system on its thermal performance are presented. Twelve typical two-dimensional air flow maldistribution models of four basic groups are considered. Convection heat transfer coefficients on both flow sides are not considered to be constants. Refrigerant side pressure drop is included in this study. The thermal performance of the evaporator and its deterioration due to this effect are determined for various conditions. The detrimental effect of the air flow nonuniformity on the thermal performance of the evaporator is found to be significant for many typical applications.