5,6-Dialkyl-7-aminotriazolopyrimidines of the formula I in which the substituents are as defined below: R<;SUP>;1 <;/SUP>;is alkyl or alkoxyalkyl, where the aliphatic groups may be substituted as defined in the description; R<;SUP>;2 <;/SUP>;is CHR<;SUP>;3<;/SUP>;CH<;SUB>;3<;/SUB>;, cyclopropyl, CH-CH<;SUB>;2 <;/SUB>;or CH<;SUB>;2<;/SUB>;CH-CH<;SUB>;2<;/SUB>;; R<;SUP>;3 <;/SUP>;is hydrogen, CH<;SUB>;3 <;/SUB>;or CH<;SUB>;2<;/SUB>;CH<;SUB>;3<;/SUB>;; processes for preparing these compounds, compositions comprising them and their use for controlling phytopathogenic harmful fungi.