The use of 5-alkyl-6-phenylalkyl-7-aminoazolopyrimidines of the formula I in which the variables are as defined below: Y is alkylene, alkenylene or alkynylene, optionally substituted by alkyl groups; R1 is halogen, cyano, nitro, hydroxyl, mercapto, alkyl, haloalkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxy, haloalkoxy, alkenyloxy, alkynyloxy, alkylthio, NRARB, alkylcarbonyl, phenyl, naphthyl, or a five- or six-membered saturated, partially unsaturated or aromatic heterocycle which contains one to four heteroatoms from the group consisting of O, N and S; RA, RB is hydrogen, alkyl or alkylcarbonyl; n is zero, 1, 2, 3 or 4; R2 is alkyl, alkenyl, cycloalkyl, alkoxyalkyl or alkylthioalkyl; R3 is hydrogen, halogen, cyano, NRARB, hydroxyl, mercapto, alkyl, haloalkyl, cycloalkyl, alkoxy, alkylthio, cycloalkoxy, cycloalkylthio, carboxyl, formyl, alkylcarbonyl, alkoxycarbonyl, alkenyloxycarbonyl, alkynyloxycarbonyl, phenyl, phenoxy, phenylthio, benzyloxy, benzylthio, alkyl-S(O)m—; m is 0, 1 or 2; A is N or C—Ra; Ra is hydrogen or alkyl; where the carbon atoms in Y, R1, R2, R3 and Ra may be substituted according to the description; for controlling phytopathogenic harmful fungi; novel 5-alkyl-6-phenylalkyl-7-amino-azolopyrimidines, processes for their preparation and compositions comprising them.