Abstract: Use of diaminopyrimidines of the formula (I) in which R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and X1, X2 and A have the meanings given in the description, and also agrochemically active salts thereof as fungicides. Diaminopyrimidines of the formulae (Ia), (Ib), (Ic), (Id), (Ie), (If) in which R8a, R8b, R8c, R8d, R8e, R8f, R3b, R3c, R3e, X1b, X1c, X1e and R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and X1, X2 and A have the meanings given in the description, and also agrochemically active salts thereof and their use for controlling unwanted microorganisms.