Micro bore finishing for metal and ceramic materials has been a challenge in the manufacturing industry. Unfortunately, little is understood about how to polish a micro bore and how to assess its inner wall quality because it is difficult to access the micro bore for either polishing or measurement. This article reports on a feasibility study of the abrasive flow polishing of micro bores of 260 similar to 500-mum diameters and 25 similar to 50 length/diameter ratios for both metal and ceramic materials. An abrasive flow polishing machine was designed and built with turbulent flow characteristics. Polishing of steel S45C bores of 400- and 500-mum diameters, stainless steel 304 bores of 500-mum diameter, and zirconia bores of 260-mum diameter was conducted. Surface roughness and topography of the polished inner walls of micro bores were characterized using profilometry and optical interferometry from the three-dimensional point of view. Significant reduction in surface roughness of the micro bore inner walls has been made in the polishing processes. The results indicate that it is feasible to apply the abrasive flow polishing technology for metal and ceramic micro bores of diameters of 260 mum or larger and the length/diameter ratios of 25 or higher. It is found that surface roughness of the polished micro bore inner walls decreases with an increase of the abrasive flow passes.