REZA KBARI
ALI VAHIDIAN KAMYAD
ALI AKBAR HEYDARI
AGHILEH HEYDARI

In this paper we study the dynamics of Hepatitis Bvirus (HBV) infection under administration of a vaccine and treat-ment, where the disease is transmitted directly from the parents tothe o spring and also through contact with infective individuals.Stability of the disease-free steady state is investigated. The basicreproductive rate, R0, is derived. The results show that the dynam-ics of the model is completely determined by the basic reproductivenumber R0. If R0 < 1, the disease-free equilibrium is globally sta-ble and the disease always dies out and if R0 > 1, the disease-freeequilibrium is unstable and the disease is uniformly persistent.