Abstract: The probability distribution of acute schistosomiasis cases is analysed with the data obtained from a pilot area. The result is not random since the variance (S2) is larger than its arithmetic mean (X). When examined by the test of goodness fit with the expected frequency of the negative binomial distribution, the result is satisfactory (X2 = 1.56, 0.30P0.20). The result of distribution fit of Poisson shows extremely significant difference (X2 = 15.51, P0.001). It shows preliminarily that the characteristics of the distribution of acute schistosomiasis cases depends on the negative binomial distribution. In studying the influence of the clustering of acute schistosomiasis cases, k may be used as an index expressing the clustering of its distribution.