  We discuss heterotic strings on Z_2 x Z_2 orbifolds of non factorisable
six-tori. Although the number of fixed tori is reduced as compared to the
factorisable case, Wilson lines are still needed for the construction of three
generation models. An essential new feature is the straightforward appearance
of three generation models with one generation per twisted sector. We
illustrate our general arguments for the occurrence of that property by an
explicit example. Our findings give further support for the conjecture that
four dimensional heterotic strings formulated at the free fermionic point are
related to Z_2 x Z_2 orbifolds.
