A medical mattress and mattress cover are disclosed, the mattress cover comprising a vapor-permeable support portion and discharge portion. Preferably the permeability coefficient of the discharge portion is much greater than that of the support portion so that water vapor passing into the cover from a user is discharged, the user and mattress remaining substantially dry. Each vapor-permeable portion may comprise a vapor permeable film supported on a textile fabric. In a second embodiment the mattress is provided with bearers defining passageways and the cover has means for passing a flow of air through the cover. This embodiment is suitable for use on an impermeable mattress support.
