The diagnosis of porcine epidemic diarrhea virus (PEDV) infection in the laboratory is rather fastidious because of difficulties in virus propagation. The feasibility of virus propagation in vivo is also limited by the handling of a number of samples at the same time. In this study, the detection of PEDV by reverse transcription polymerase chain reaction (RT-PCR) is described. The RT-PCR could detect up to 10⁴ TCID ₅₀/ml of PEDV and did not show any cross reaction with transmissible gastroenteritis virus or porcine rotavirus. Using this method, the detection of PEDV in experimentally inoculated piglets was possible as early as one day after inoculation. These results suggest that the RT-PCR could be applicable for a rapid diagnosis of PEDV infection.