In this paper, the performance of flat plate finned tube heat exchangers operating under frosting conditions was investigated experimentally. Heat exchangers of single and multiple tube row(s) were tested to show the effects of various parameters on heat transfer performance. The parameters include temperature and relative humidity of air, flow rate of air, refrigerant temperature. fin pitch. and row, number, The time variations of heat transfer rate, overall heat transfer coefficient, and pressure drop of heat exchangers presented.