The present invention relates to stable compositions for the fungicidal equipment of thermoplastic polymers, in particular PVC, comprising thiabendazole, at least one iodine-containing fungicide and at least one epoxide and optionally further fungicidally active compounds, and also to methods for preparing these formulations and to uses thereof for the protection of thermoplastic polymers against attack and destruction by microorganisms. Moreover, the invention relates to mold-resistant PVC materials equipped with the compositions according to the invention.