Novel isothiazolecarboxamides of the formula (I) wherein R1 represents a hydrogen atom or cyanomethyl, R2 represents a hydrogen atom or methyl, and R3 represents a hydrogen atom, C¿7-10? alkyl or methoxycarbonylphenoxymethyl, provided that R?1, R2 and R3¿ are not simultaneously a hydrogen atom, a process for the preparation of the new compounds and their use as microbicides