Thermal hadron production in high energy collisions

It is shown that hadron abundances in high-energy , pp and collisions, calculated by assuming that particles originate in hadron-gas fireballs at thermal and partial chemical equilibrium, are in very good agreement with the data. The freeze-out temperature of the hadron-gas fireballs turns out to be nearly constant over a large centre-of-mass energy range and not dependent on the initial colliding system. The only deviation from chemical equilibrium resides in the incomplete strangeness phase-space saturation. Preliminary results of an analysis of hadron abundances in S+S and S+Ag heavy-ion collisions are presented.