A knife holder device for a microtome having a blade guard constituted as a pivotable bow, wherein, in a protective position, the blade guard is disposed on the side of the knife facing away from the sample at a distance such that access to the cutting edge is not possible. The blade guard can be positioned in three different defined positions and is provided with elements that have the following effects depending on the position: in the upper, protective position, simultaneous fixing of the position of the knife holder in the guideway; in the central, knife-holder-sliding position, accessibility to the knife holder with simultaneous release of the position fixture of the knife holder in the guideway; and in the lower, knife-changing position, free accessibility to the knife holder with simultaneous fixture of the position of the knife holder in the guideway.