A device and a method for disinfecting a microtome cryostat with introduction of a disinfection agent (3) into the cryostat chamber (2), action of the disinfection agent on the cryostat chamber, removal of the disinfection agent (3) by precipitation in a colder area (6) and drainage away from there. To enable such a microtome cryostat (1) to be disinfected several times per day without prolonged interruption of operation, a disinfection agent is used (3) that is effective below 0° C. and is introduced as a mist into the cryostat chamber (2) at below 0° C., the disinfection agent (3) being effective as a frost deposit in the cryostat chamber, wherein the frost deposit is displaced into a colder area (6) by sublimation and is converted to liquid by sporadic defrosting phases of this area (6) and thus removed.