The invention relates to microbicidal preparations which comprise a) at least one of 1,2-benzisothiazolin-3-one and its derivatives, b) at least one of 2-mercaptopyridine N-oxide, its salts and derivatives and c) at least one alkalinizing agent, or which are prepared by mixing components a) to c), where the preparations have a pH of at least 11. The preparations are characterized by the fact that they are clear and storage-stable, and they are suitable for use as preservatives.
