  We discuss a duality of (0,2) heterotic string vacua which implies that
certain pairs of (0,2) Calabi-Yau compactifications on topologically distinct
target manifolds yield identical string theories. Some complex structure moduli
in one model are interpreted in the dual model as deforming the holomorphic
structure of the vacuum gauge bundle (and vice versa). A better understanding
of singularity resolution for (0,2) models may reveal that this duality of
compactifications on singular spaces is part of a larger story, involving
smooth topology-changing processes which interpolate between the (0,2) models
on the resolved spaces.
