Abstract. Explicit Lyapunov functions for SIR and SEIR compartmental epidemic models with nonlinear incidence of the form βI p S q for the case p ≤ 1 are constructed. Global stability of the models is thereby established.1. Introduction. It is traditionally postulated that the spread of an infection occurs according to the principle of mass action and associated with it the bilinear incidence rate. However, there are a variety of reasons why this standard bilinear incidence rate may require modification. The incidence rate of the form βI p S q , were S and I are respectively the number of susceptible and infective individuals in the population (or the fractions of susceptible and infective), and β, p and q are positive constants, is the most common nonlinear incidence rate. In recent years models with this incidence rate were considered by several authors, for example Liu et al. [11,12] In this note applying the direct Lyapunov method, we consider global properties of SIR and SEIR models with the incidence rate of the form βI p S q for the particular case p ≤ 1. We construct a Lyapunov function which is a generalization of the Lyapunov functions constructed earlier for models with bilinear incidence [10,8]. We show that the condition p ≤ 1 is a sufficient condition for global stability, and that the global properties of the systems do not depend on the value of q.