A reverse transcription polymerase chain reaction ( RT-PCR) was used for detection of infectious hypodermal and haematopoietic necrosis virus ( IHHNV) from the gills and subcutaneous tissue of Penaeus vannamei ( 10- 15cm in body size) without clinical signs. With primers 77012R and 77353F, a fragment of 356bp of IHHNV was amplif ied in RT-PCR. The amplified product was sequenced and showed more than 98% homologue with the sequences of other IHHNV strains in Gene Bank.