An epidemiological survey on 136 inhabitants of a Gum-River basin, Hyunbook-ri, Puyo-up, Puyo county, South ChoongCheong-Do, conducted from July 22, 1981 to July 25, 1981 with the purpose of studying Clonorchiasis, revealed the results as follows, 1. Positive skin reaction (wheal size larger than $60mm^2$) rate was 42% (55 positive reactors among the 131 studied), and the positive rates were all high at the age groups over twenty, while low at the below twenty. 2. In the stool examination, the employed cellophane thick smear method revealed the results as follows, overall infection rate of helminth: 65% (55 infected among 84 studied) - C. sinensis 33% (28/84), A. lumbricoides 5% (4/84), Taenia Sp 7% (6/84), T. trichiurus 32% (27/84). 3. The prevalence rate of C. sincrisis was highest in 40 - 49 year-old group by age: male 39% (11 infected/ 28 studied) female 14% (3/28), and not a single case was found in the lower age groups than twenty including