The focus of process chemistry is toward pilot-and full-scale production. As a result, this chapter will address the topic of scale-up of microwave-promoted chemistry. Microwave heating is used on very large scales in industries such as drying, polymer and rubber preparation, and food processing,1 as well as on more moderate scales for niche applications in analytical, environmental, and biomedical chemistry. However, the examples presented here will be drawn mainly from pharmaceutical process chemistry2 derived from traditional organic synthesis and particularly the chemistry of drug discovery, since this is from where process chemists get their target molecules and often their rst synthetic route. Microwave heating is relatively expensive compared to other types of conventional, conductive heating methods. Bogdal has listed some of the attractive features of microwave heating and concluded that to be commercially competitive, it must be applied to high-value products.3 This ts well with the manufacture of high-value, low-tonnage pharmaceuticals rather than low-value, high-tonnage agrochemicals and commodity chemicals. Other highvalue products are polymers and peptides (effectively biopolymers), which also benet from microwave heating and may be scaled up in a limited sense.