Abstract. Existence and asymptotic stability of the periodic solutions of the Lipschitz system x (t) = εF (t, x, ε) is hereby studied via the averaging method. The traditional C 1 dependence of F (s, ·, ε) on z is relaxed to the mere strict differentiability of F (s, ·, 0) at z = z 0 for ε = 0, giving room to potential applications for structured nonsmooth systems.