  The production of K+ and of K- mesons in heavy-ion collisions at beam
energies of 1 to 2 AGeV has systematically been investigated with the Kaon
Spectrometer KaoS. The ratio of the K+ production excitation function for Au+Au
and for C+C reactions increases with decreasing beam energy, which is expected
for a soft nuclear equation-of-state. A comprehensive study of the K+ and of
the K- emission as a function of the size of the collision system, of the
collision centrality, of the kaon energy, and of the polar emission angle has
been performed. The K-/K+ ratio is found to be nearly constant as a function of
the collision centrality and can be explained by the dominance of strangeness
exchange. On the other hand the spectral slopes and the polar emission patterns
are different for K- and for K+. Furthermore the azimuthal distribution of the
particle emission has been investigated. K+ mesons and pions are emitted
preferentially perpendicular to the reaction plane as well in Au+Au as in Ni+Ni
collisions. In contrast for K- mesons in Ni+Ni reactions an in-plane flow was
observed for the first time at these incident enegies.
