Manufacturing processes seldom run perfectly. In attempts at improvement, these processes are continually“adjusted”by the mechanic, supervisor, and engineer; or more formally, they are“studied”from manufacturing, quality control, or engineering perspectives. These studies may be generically categorized as process quality optimization studies. Four such studies are defined, explained, and compared in this article. These are the process performance check, the process performance evaluation, the process capability study, and the process improvement program. In addition it is shown how these studies are used, separately or in combination, to achieve process quality optimization systematically, effectively, and at minimum cost.