Examinations were performed on 351 individuals of Shikishima village, Yamanashi Prefecture. Three fecal samples were collected at one-week intervals and examined by MIFC method without iodine. Reactions with a diameter of 9 mm or more in wheal and/or 20 mm or more in erythema were regarded as the positive for the intradermal reaction using Melcher's antigen (1 : 1,000). For the COP test, each one drop of serum and a saline suspension of eggs were mixed on a microscope slide and sealed a coverslip with vaseline. The number of eggs showing precipitates were counted after 48 hrs at 37 degrees C. The results showed that all the precipitates were small in size in the COP titer less than 40%. Medium precipitates appear first in the cases of a 40.% class and the percentage increased thereafter as the COP titer increased. Large precipitate was found in 10% of the eggs affected in a 50% class and found in 40% in the titer of a 80% class. Of 351 tested, a significant higher rate of egg-passers (42.7%, 41/96) was obtained in the COP reactors, as compared with other two groups; 19.4% (41/211) in the dermal reactors, 11.7% (41/351) in the total subjects. Moreover, the egg-passers were recovered in 60--70% of the cases in the COP titer of more than 70%. It was considered that the COP test was a useful diagnostic method for schistosomiasis japonica and the sensitivity and efficiency of this test were superior to those of intradermal test with regarded to the screening of the subjects for fecal examination.