In this article, we provide a brief summary of study design of case-control study within a cohort and an introduction of two case-control studies within a cohort conducted in Japan recently using antihypertensive drug database based on the post-marketing surveillance data of pharmaceutical companies. In the case-control study within a cohort, it is possible to avoid bias caused in a case-control study and conduct more efficiently than cohort study. Therefore the case-control study within a cohort widely has been used in pharmacoepidemiological studies with a database. (Jpn J Pharmacoepidemiol 2013; 18(2): 77-83)