The invention relates to a microtome, in particular a rotary microtome (1), comprising a micrometer mechanism (3) having a drive (2) for producing a relative movement between an object holder (4) and a blade and a positioning device acting on the micrometer mechanism (3) to influence the relative movement, the positioning device comprising an advancing device (6) and a trimming device (7) interacting with the advancing device (6), said microtome being designed and modified with regard to a simple and reliable adjustment of the trimming device (7) as well as activation/deactivation of a retraction by structurally simple means in such a way that the positioning device has a combined actuating device (8) for both an adjustment of the trimming device (7) and also an activation/deactivation of a retraction which can be carried out by means of the advancing device (6).