An important problem at present is the contamination of drinking water. In this paper, the author will focus on the parasitic contamination in water and further implication on human health. The important parasites that are usually mentioned as major contaminants will be briefly reviewed. In addition to water contamination, soil contamination is another important problem. Basically, soil contamination with pathogenic parasite is a big public health problem in tropical developing countries. Diseases transmitted by soil are common in many tropical areas, including Thailand. In this article, the author summarized the prevalence of soil contamination with pathogenic parasite in Thailand. According to analysis, overall prevalence of contamination is equal to 7.8 %. There is no significant correlation between setting and prevalence.