The sera from 25 patients with acute, 36 patients with chronic schistosomiasis japonica and 68 patients with pagumogonimiasis skrjabini were tested against SEA, schistosome egg, Paragonimus adult antigen (PAA) and Paragonimus metacercaria using different tests including biotin-avidin system (BAS), ELISA, circumoval precipitate reaction (COPT) and metacercaria membrane reaction (MCMR). Results showed: 1. The specific reactions using PAS and ELISA were (1) both 100% in acute schistosomiasis patients (ASP), (2) 100% and 97.2% respectively in chronic schistosomiasis patients (CSP) and (3) both were 98.5% in paragonimiasis patients (PP). 2. The cross reactions using BAS, ELISA and MCMR were (1) 76%, 72% and 20% respectively in ASP, (2) 27.8%, 22.2% and 19.4% respectively in CSP. 3. The cross reactions using BAS, ELISA and COPT were 26.5%, 30.9% and 8.8% respectively in PP. 4. The frequency of cross reaction was related to the sensitivity of the test used. 5. The frequency of cross reaction in ASP was remarkably lower with MCMR than with BAS or ELISA. 6. The frequency of cross reaction in CSP was related to the intensity of infection. 7. We suggest that more than one test should be carried out in patients who showed cross reaction to a single test, then the frequency of cross reaction would decline.