A formula for variance effective population size (N-e) for analysis of mitochondrial genes is derived and discussed. Only the female part of the population is taken into account; hence, N-e is, in the given case, the effective number of females. N-e = m(2)(N - 1)/sigma(2), where N is the number of females, sigma(2) is the variance of the reproductive contributions of individual females (measured as the number of their daughters that are part of the next generation), and m is the mean number of daughters per female.