The Individual Pension System is a strategic mechanism that enables individuals to maintain their level of well-being during retirement at the same level as during their active working life, and contributes to economic stability by converting long-term savings into investments at the macroeconomic level. The Individual Pension Savings and Investment System Law (BES Law) was published in the Official Gazette dated April 7, 2001, and numbered 24366. With this BES Law, the individual retirement system (BES) came into effect. Within this framework, the system, whose legal infrastructure was established, became active in 2003 with the commencement of operations by retirement companies. It can be stated that the financial sustainability of the individual retirement system and the level of well-being it promises to its participants are directly related to the performance of retirement investment funds, which are the fundamental building blocks of the system. These funds, which act as a bridge in transferring individual savings to capital markets, differ from direct capital market instruments in terms of risk, return, and liquidity characteristics. The aim of this study is to examine the general characteristics of retirement investment funds in the BES and to present the relationship between the structural characteristics and returns of these funds within a theoretical framework.