Fungicidal mixtures comprising, as active components, 1) the triazolopyrimidine derivative of the formula 1, and 2) phosphorous acid H.sub.3PO.sub.3, its alkali metal or alkaline earth metal salts or derivatives releasing them II in a synergistically effective amount, methods for controlling harmful fungi using mixtures of the compound I with the compound II, the use of the compound I with the compound II for preparing such mixtures and compositions comprising these mixtures are described.