In Chapter 4, Section 4.2, a general discussion of factorial experiments was presented. Whereas the meaning of factorial experiments is that all possible combinations of the levels of the factors exist in the experiment, this in no way describes the design of the experiment as dictated by the randomization of the combinations onto the experimental units. Hence, “factorial” refers only to the type of experiment and not to the design or layout. In this chapter the special case in which all factors of a factorial experiment have only two levels is described and the design is assumed to be completely randomized within each block.