  We present the analytic calculation of the Master Integrals for the two-loop,
non-planar topologies that enter the calculation of the amplitude for top-quark
pair hadroproduction in the quark-annihilation channel. Using the method of
differential equations, we expand the integrals in powers of the dimensional
regulator $\epsilon$ and determine the expansion coefficients in terms of
generalized harmonic polylogarithms of two dimensionless variables through to
weight four.
