Main results coming from the extensive study of strangeness signals from heavy ion collisions at the CERN SPS energy range are discussed. A systematics of production rates is given, as a function of strangeness content of the products, and of the incident energy, centrality and the mass of the colliding nuclei. Different interpretations of the results are briefly discussed.

PACS numbers: 25.75.-q, 12.38.Mh