This chapter examines the role of guarantees in retirement savings arrangements, in particular minimum investment return guarantees during the accumulation phase. The main goal is to assess the costs and benefits of different return guarantees. The analysis uses a stochastic financial market model where guarantee claims are calculated as a financial derivative in a financial market framework (like e.g. the valuation of a put option). In this context, the chapter highlights the value of capital guarantees that protect the nominal value of contributions in pension plans. However, such guarantees can only be introduced relatively easily in the very specific context considered in this chapter. Allowing plan members to vary contribution periods or investment strategies, or change providers, would raise major challenges for an effective and efficient implementation of return guarantees. It would increase the complexity and cost of administering the guarantee.