There is a great need for prevention against parasitosis in the field of community health, though in actual practice, the mass examination for parasite carriers has not succeeded to get enough rate of receiving the examination. Because of this problem the author has investigated the conditions the performance of health practice against parasitosis, systematically. In order to get some criteria for the evaluation of the parasite control in communities, the author has investigated statistically the results of parasitic egg examination among general residents comparing to those of the school children at the same communities on O-prefecture. The objects were selected among the areas in this prefecture officially designed for "the promotion of preventive practice against ancylostomiasis". The studies have been carried out statistically and the results checked by the field surveys to learn the social factors influencing the receiving rate of examination and the efficiency of the practice. The results of the studies have been as follows: 1) By examining annual change of correlation between the rates of general residents and those of the school children in the same communities, there have been observed differences among the kinds of parasites. 2) Concerning "the special areas for preventive practice against ancylostomiasis" the parasite carries among the children has showed high correlation with those among general residents at the beginning of the designation as the special areas. This correlation has changed as the preventive practice proceeded. About ascariasis and other parasitoses, the correlation between the children and general residents have maintained relatively unchanged in high value. The differences of the elapse between the numbers of ancylostomiasis and the others could be derived from the ecological specialities and the mode of infection. 3) Correlation between the residents and children was high in ancylostomiasis when the receiving rate was over 80% and the same could be said in ascariasis when it was over 60%. 4) Also high correlation were observed between 1 to 3% of ancylostomiasis among school children, and under 15% of ascariasis among them. 5) These statistical results have been investigated expecting to get some criteria for evaluation of preventive practice. 6) The results of field survey about factors influencing on these data have been described.