ABSTRACT Bioequivalent medicinal products have an important role on health systems and especially on health economics. Generic drugs are produced in order to be used interchangeably with other drugs in the clinic. It is obligatory to comply with the guidelines of regulatory authorities in the production and licensing of the generics of original medicinal products whose patents have expired by the pharmaceutical  industry. One of the most important steps of these guidelines is the selection of a reference product. In the guidelines of World Health Organization (WHO) and some other countries, the term comparator is used instead of the reference product. The term comparator represents the pharmaceutical product for which the generic may be used interchangeably. Pharmaceutical products where the generic product can be used interchangeably in the clinic, in case an innovative product is removed from the market are defined as comparator products. The selection of the reference products to be used in the production of generic medicinal products for human use still maintains its current importance. In this chapter; the criteria used by the national regulatory authority, Turkish Medicines and Medical Devices Agency (TMMDA) in selection of reference products for the development of bioequivalent drugs will be reviewed together with those in some international guidelines and some advices regarding the issue will be provided.