  We calculate the full second-order radiation transfer function for Cosmic
Microwave Background anisotropies on large angular scales in a flat universe
filled with matter and cosmological constant. It includes (i) the second-order
generalization of the Sachs-Wolfe effect, and of (ii) both the early and late
Integrated Sachs-Wolfe effects, (iii) the contribution of the second-order
tensor modes, and is valid for a generic set of initial conditions specifying
the level of primordial non-Gaussianity.
