Principles for Polycrystalline Diamond Compact (PDC) bit design are discussed here. Each of these factors must be considered on an application-to-application basis to ensure achievement of rate of penetration (ROP) goals during cooling, cleaning the bit, and removing cuttings efficiently. During design, all factors are considered simultaneously. Cutting structures must provide adequate bottomhole coverage to address formation hardness, abrasiveness, and potential vibrations and to satisfy productive needs. Early (1970s) PDC bits incorporated elementary designs without waterways or carefully engineered provisions for cleaning and cooling.