Chemical milling has been used to advantage in removing excess material and reducing the overall weight of metal parts. It is a valuable complementary technique to conventional milling and machining methods and is particularly useful for removing metal from thin sections or from parts that are already shaped. The first section of this report discusses chemical milling generally, describing the process, its applications, advantages and limitations, chemical milling solutions, maskants, and various other aspects of the chemical milling process. The second section considers the effectiveness of chemical milling for some specific materials: aluminium, beryllium, magnesium, titanium, steel, and some stainless steel alloys. Various chemical milling solution formulations are presented and effects on such factors as mechanical and fatigue properties are considered.