ASTM F 55 material specification was issued in 1965 to cover the metallurgical requirements of Type 316/316L stainless steel bar and wire for the manufacture of surgical implants. Eventually, it was recognized that austenitic implant stainless compositions with well defined nonmetallic inclusion limits would be desirable. The low carbon 316L alloy with specified inclusion limits emerged as the most widely used implant quality stainless material over the last 30 years. Microstructural requirements include a fully austenitic microstructure that is free of delta ferrite when examined at 100X magnification and an ASTM grain size of five or finer. The importance of low sulfur content, effect of secondary phases, intergranular corrosion resistance, and the compositional requirement %Cr + 3.3 × %Mo ⩾ 26 are highlighted. Various clinical factors are discussed relative to the microstructural features of implant quality 316L.