6-(2,4,6-Trifluorophenyl)triazolopyrimidines of the formula I in which the substituents have the following meanings: R1 is alkyl, haloalkyl, cycloalkyl, halocycloalkyl, alkenyl, haloalkenyl, cycloalkenyl, alkynyl, haloalkynyl, cycloalkynyl, phenyl, naphthyl or a five- or six-membered saturated, partially unsaturated or aromatic heterocycle comprising one to four heteroatoms from the group consisting of O, N and S, R2 is hydrogen or one of the groups mentioned in R1, R1 and R2 can also, together with the nitrogen atom to which they are bonded, form a five- or six-membered ring which is interrupted by an atom from the group consisting of O, N and S, and/or R1 and/or R2 can be substituted according to the description; X is cyano, C1-C4-alkoxy, C3-C4-alkenyloxy, C1-C2-haloalkoxy or C3-C4-halo-alkenyloxy; process for the preparation of these compounds, preparations comprising them and their use in the control of harmful phytopathogenic fungi.