This paper describes the scale-up of a highly exothermic and fast reaction from a microreactor with an internal volume of less than 1 mL to a mesoreactor with an internal volume of 13.5 mL. The development of a continuous process for manufacturing a ketone from an ester using a Grignard reagent is described. The different steps undertaken and the considerations made to be able to operate in continuous mode and achieve a product output of ca. 0.5 kg are presented.