An improved two-step replication process for fabrication of porous metallic membranes is provided. A negative of a porous non-metallic template is made by infiltration of a liquid precursor into the template, curing the precursor to form a solid negative, and removing the template to expose the negative. Metal is deposited to surround the exposed negative. Removal of the negative provides a porous metallic membrane having pores which replicate the pores of the original template membrane. The negative is kept immersed in a liquid at all times between removing the template and depositing the metal. This immersion eliminates damage to the negative that would be incurred in drying the negative out between these processing steps. Another aspect of the invention is metallic membranes prepared according to the preceding method. For example, metallic membranes having pores smaller on one side than on the other side of the membrane are provided.