The science of quality control is largely statistical in nature, and entire books have been devoted to the application of statistical techniques to quality control. Statistical quality control is a key factor in process validation and the manufacture of pharmaceutical products. In this chapter we discuss some common applications of statistics to quality control. These applications include Shewhart control charts, sampling plans for attributes, operating characteristic curves, and some applications to assay development, including components of variance analysis. The applications to quality control make use of standard statistical techniques, many of which have been discussed in previous portions of this book.