In this paper we use the method of layer potentials to study L 2 boundary value problems in a bounded Lipschitz domain Ω for a family of second order elliptic systems with rapidly oscillating periodic coefficients, arising in the theory of homogenization. Let L ε = −div A(ε −1 X)∇ . Under the assumption that A(X) is elliptic, symmetric, periodic and Hölder continuous, we establish the solvability of the L 2 Dirichlet, regularity, and Neumann problems for L ε (u ε ) = 0 in Ω with optimal estimates uniform in ε > 0.