[en] Relativistic heavy ion collisions provide, in principle, necessary conditions for the formation of the quark gluon plasma. Strangeness enhancement was amoung the announced specific signals expected from this new, hypothetical state of nuclear matter. Analysis of the first generation of experiments with light and medium sized ions have been completed. Results ''on strangeness production become precious handles to study in great detail what is actually happening. The current experimental situation is assessed. The emerging picture is still incomplete: however, open questions constrain requirements on future heavy ion experiments