In all application areas of immunoassays, the long-term stabilization of the used bio-components is a sensible and helpful measure which allows for simple and time-saving work. It is also often the mandatory prerequisite for a successful assay execution. Especially for commercial assays which are used, for example, in in vitro diagnostics or food analytics, sufficient stability of the assay components is a prerequisite for the market launch of these products. Stabilization in this context means the extension of shelf lifeShelf life and protection against denaturation of the assay components depending on time and temperature. This includes capture antibodies, internal standards and controls, as well as enzyme-labeled detector antibodies. Well-stabilized assays achieve shelf lives of several years. This chapter describes how to stabilize the individual assay components and provides guidance on the experimental procedure in the context of assay development.