Through-hole diamond membranes with submicrometer-sized pores were fabricated by oxygen plasma etching through an anodic porous alumina mask. Polished polycrystalline diamond film (3 mum thick) was covered with the porous alumina mask and was etched for about 10 min. The resulting diamond membrane after separating from Si had a pore size of about 300 run diam and a pore density of 5.7 x 10(12) mm(-)2. This technique is simple and allows the controlled preparation of through-hole diamond membranes by varying the dimensions of the alumina mask. These membranes are useful for several applications, including filtration and How-through electrolysis.