Strangeness production at incident energies close to the elementary production threshold is considered a tool to extract information about the properties of the hot and dense state of nuclear matter produced as a transient state in heavy ion collisions. The production yields and azimuthal anisotropies of strange particles available for nucleus nucleus collisions from the KaoS and FOPI experiments at the SIS accelerator of GSI, Darmstadt, are reviewed with respect to their significance of possible in-medium modifications and their sensitivity to the nuclear equation of state. ©2001 American Institute of Physics.