Abstract: This paper deals with the site of Clonotchis worm antigen skin test and the duration of positive skin reaction studied during surveys on clonorchiasis in the suburbs of Beijing. The results are as follows:1. In 124 inhabitants in an endemic area, intradermal tests with the same Clonor-chis antigen were performed on 3 different sites of the skin at the same time, namely the flexor surface of forearm, the extensor surface of forearm and the interscapular region on the back. After statistic treatment, the skin positive rates among 3 sites showed no significant difference, but the ova positive rate was much higher in persons with positive reaction in all 3 sites than in those with positive reaction in only 1 or 2 sites. No case of ova positive was found in those who were negative in all 3 skin sites.2. 100 persons were re-examined 7 years later by the same method with the same antigen. It revealed that following the cure of Clonorchis infections with proper treatment, the original positive skin reaction in most cases had changed to negative, while in most untreated or treated but not cured cases, the skin test remained positive.