Data are presented on the dynamics of the cestode Ditestolepis diaphana (Colodkowsky 1906) abundance in the common shrew (Sorex araneus L. 1758) population in Karelia. It is shown that the abundance of cestodes parasitizing in shrew intestines in the habitats investigated conforms to the negative binomial distribution (NBD). Estimating distribution parameters we get statistically reliable indicators of the parasite abundance, and postulate steady relationships to exist in the host-parasite system (a balance of host individuals resistant or non-resistant to the infestation).