Abstract
In this paper we extend the Lyapunov functions, constructed by A. Ardito and P. Ricciardi for predator-prey system [1], to the three level food chain models. We first consider a general three-level food-chain model. A criterion for the extinction of top predator will be given. Then we restrict our attentions to the case in which the prey is of logistic growth and predators have Holling's type II functional responses. © Springer-Verlag 1998.