Abstract: Indirect immunoperoxidase staining technique using frozen sections of adult worm as antigen (ⅡP-AWA) was carried out to detect antibodies against schistosome antigens (AWAb) for the diagnosis of existing infection of schistosomiasis in COPT positive cases. Sera from 229 COPT positive and 135 COPT negative cases in Shanghai County, where schis-tosomiasis had been eradicated for more than 5 years, were tested. Sera from 122 patients with positive stool hatching from an endemic area were served as positive controls. The positive rates of the three groups were 96.9%, 5.2%, and 100% respectively. The staining pattern of the worm sections was mainly diffused at serum dilutions 1:4 to 1:16.149 sero-positive cases were treated with pyquiton (60mg/kg-2d) and re-examined 1, 1.5. and 2.5 years post-treatment. The negative conversion rate of HP-AWA was consi-derably higher than that of COPT (80% vs. 61.1%) at the first year, but no significant difference was observed after 2.5 years (85.5% vs. 83.6%). With the decreasing antibody titer, the staining pattern of worm sections changed from diffused to focal pattern, mostly in the gut.The results suggest that the presence of detectable AWAb in untreated patients of patients treated 2 years ago with pyquiton possibly indicate latent schistosomiasis. ⅡP-AWA is of practical value in screening populations for latent schistosomiasis in areas where the disease had been under control.