For the molecular detection of Sweet potato feathery mottle virus (SPFMV) from diseased sweet potato plants, reverse transcription and polymerase chain reaction (RT-PCR) was performed with the use of a set of virus-specific primers to amplify an 816 bp product. The viral coat protein gene was selected for the design of the primers. No PCR product was amplified when Turnip mosaic virus, Potato virus Y, or Cucumber mosaic virus were used as template in RT-PCR with the SPFMV -specific primers. The lowest concentration of template viral RNA required for detection was 10 fg. The virus was rapidly detected from total nucleic acids of leaves and roots from the virus-infected sweet potato plants as well as from the purified viral RNA by the RTPCR. Twenty-four sweet potato samples were selected and analyzed by RT-PCR and restriction fragment length polymorphism (RFLP). RFLP analysis of the PCR products showed three restriction patterns, which resulted in some point mutations suggesting the existence of quasi-species for the virus in the infected sweet potato plants.