In the sixty years since age-hard-enable, nickel-base superalloys were first identified, the compositional and microstructural features of these high-performance metals have changed markedly—from the early Nimonic (INCO trade name) 80A (a wrought alloy of essentially four elements) to today’s family of wrought from ingot, powder metal, cast and directionally cast alloys. As a result of physical property refinements, the alloys’ characteristics can be tailor fit to specifically defined applications. With this range of possibilities available, it is necessary to consider the appearance and implications of microstructural defects—defects which have accompanied advances in processing and materials selection. As new alloys and processes are developed, industry must correspondingly commit to identifying and controlling new defects.