A porous polytetrafluoroethylene (PTFE) structure particularly for use as a liquid filter comprises particles of granular-type PTFE fused together to form a porous integral network. The structure is formed by spraying an aqueous suspension of granular PTFE particles and baking at a temperature of 335 DEG -350 DEG C. Typically the specific gravity is 0.8 to 1.54. The crystallinity is less than 95%. The structure may be supported on a perforate substrate such as stainless steel mesh.
