The spatial distribution of perithecia of Phyllactinia moricola(P. Henn.) Homma wintering on mulberry twigs was well fitted by the mathematical modelvof negative binomial distribution. Fitting a common index of dispersion k_c, however, was impossilble to all series of negative binomial distributions. The method of Nass provided a suitable goodness-of-fit criterion for the negative binomial distribution when expectations are small.