Juvenile Penaeus japonicus were experimentally infected by feeding minced shrimp tissue of WSSV-infected .The experimental shrimps were sampled everyday and whole body of the shrimp was cryosectioned then WSSV was detected by FAT method using monoclonal antibodies in order to explain the virus development in shrimp body .The results indicated that in the first three days post-infection the virus was not detected in any samples ;on the forth day the virus was first detected in hemacyte in gill cavity ;on the fifth day it developed to gill tissue , epidermal tissue and hemal sinus ; on the sixth day to stomach and heart ;on the seventh day to lymphoid organ and mid-gut ;on the eighth and ninth days to all the detected tissues but not to the hepatopancreas .