A mattress cover, especially for hospital mattresses prevents the ingress of liquids to the mattress core. The mattress cover includes an opening to allow the cover to be put on, and taken of, a mattress core. The opening is closed by a zip fastener (10). The teeth (12) of the zip fastener (10) are mounted on a substrate which is impermeable to fluids. Preferably the substrate is coated with a polyurethane material (14). The teeth (12) of the zip fastener are directed inwardly towards the mattress core and the substrates act to cover the zip when closed, thereby substantially preventing the ingress of fluids through the zip. The opening is also provided with a cover flap which is constructed so that there are no exposed puncturing joins (such as are generated by stitching) which would allow the ingress of liquid.