  The dependence of K+ production on the nuclear equation of state is
investigated in heavy ion collisions. An increase of the excitation function of
K+ multiplicities obtained in heavy (Au+Au) over light (C+C) systems when going
far below threshold which has been observed by the KaoS Collaboration strongly
favours a soft equation of state. This observation holds despite of the
influence of an in-medium kaon potential predicted by effective chiral models
which is necessary to reproduce the experimental K+ yields. Phase space effects
are discussed with respect to the K+ excitation function.
