Immuno-blot was used in diagnosis of schistosomiasis japonica using diagnostic 31/32 KD proteins in S.japonicum Among 52 confirmed schistosemiasis cases 100% showed positive reaction while none of the sera of 20 normal control reacted. No cross reactions occured with sera from 36 paragonimiasis; 26 cysticercosis and 50 trichinelliasis cases. However, 11.5-58.3%cross reactions were found with above sera in IHA and ELISA. The diagnostic value of immuno-blot and 31/32 kD schistosome proteins were confirmed.A field application of immuno-blot in diagnosis of schistosomiasis japonica was performed. The positive rates in immuno-blot and IHA were 58.1% and 54.4% respectively in 136 cohorts with and without past history of schistosomiasis in the endemic area. It was found that immuno-blot was highly sensitive, specific and reproducible.It was easy to perform and suitable for field use.