The Eu1−xGdxS system goes from ferromagnetism for small x to antiferromagnetism for large x[1]. We have studied the specific heat and the magnetic properties of that system in the concentration range where the Curie‐Weiss temperature, &Vthgr;, changes sign. Both measurements clearly indicate a spin‐glass freezing for x ∼ 0.5 and a mixed state for x ≳ 0.6. Ferromagnetic clusters have been observed in both the spin‐glass and in the mixed regimes.