Infection rates with white spot syndrome virus (WSSV) in 4 small penaeid shrimp species, Metapenaeopsis acclivis, M. barbata, M. dalei and Trachypenaeus curvirostris collected from the western Seto Inland Sea of Japan, was examined by PCR, and transmission of the virus to juvenile Penaeus japonicas was tried by oral or intramuscular inoculation of infected samples. No shrimp collected from the Aki-Nada and Iyo-Nada regions were shown to carry WSSV, except 2 out of 274 individuals of M. dalei from Iyo-Nada. Infection rates of M. acclivis, M. barbata and T. curvirostris collected from the Suo-Nada region were 29, 40 and 23%, respectively. Oral administration of small pieces of PCR positive shrimp muscle did not kill any challenged shrimp during the test period, but could establish infection with WSSV. Half of the challenged shrimp injected with a filtered homogenate of PCR positive shrimp muscle died with typical signs of WSS within 11 days.