Abstract: Imidazo [1,5-a] pyrimidine derivatives of the formula (I) exhibit antifungal properties: ##STR1## wherein X.sub.1 and X.sub.2 are selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxy group, an amino or substituted amino group, an alkoxy group, an alkylthio group, an alkylsulfinyl group and an alkylsulfonyl group; R.sub.1, R.sub.2 and R.sub.3 are selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group and an aralkyl group.Compound (I) are prepared by reacting the corresponding .alpha.-acylamino-alkylpyrimidines with condensing agents to form chlorine-substituted imidazo [1,5-a] pyrimidines, then replacing one or both chlorine atoms in the pyrimidine ring with other substituents, if necessary.