Most plants of commercial poinsettia cultivars grown from cuttings develop mosaic and chlorotic dot symptoms on leaves. Reverse transcription-polymerase chain reaction (RT-PCR) test showed that they were infected with Poinsettia mosaic virus (PnMV). In a survey of commercially grown poinsettias conducted in Korea, PnMV was detected in ten of ten poinsettia cultivars sampled and in 100% of 178 samples tested. The virus has isometric particles and about 29 nm in diameter. Crystalline virus particles were observed in cytoplasm of cells of diseased plants by transmission electron microscopy. Nucleotide sequence of coat protein gene of PnMV-K1 showed 97.3% homology with that of a German isolate. This is the first report on PnMV in Korea.