Prescription switch is a phenomenon of major interest for most of current questions in pharmacoepidemiology and pharmacoeconomics. However, only a few drug utilization studies focus on prescription switch description and analysis. Prescription switch can be considered at two different levels: global (drug market changes) or individual (description of patient's treatments patterns). The objective of this article is to describe the different types of prescription switch studies, according to this distinction. Objectives, type of data needed, and limits of each type of prescription switch study are presented.