  We discuss a notion of large complex structure for elliptic K3 surfaces with
section inspired by the eight-dimensional F-theory/heterotic duality in string
theory. This concept is naturally associated with the Type II Mumford partial
compactification of the moduli space of periods for these structures. The paper
provides an explicit Hodge-theoretic condition for the complex structure of an
elliptic K3 surface with section to be large. We also discuss certain
geometrical implications of this large complex structure condition in terms of
the Kodaira types of the singular fibers of the elliptic fibration.
