Genetic variation plays a significant role in the normal functioning of the immune system, and also in the interaction between many common drugs and cellular pathways. With a growing number of cytokine-based therapies now in mainstream clinical use, the prospect of targeting these agents to the individuals likely to benefit from them most is an appealing one. This review outlines the potential clinical impact of cytokine pharmacogenetics in targeting these therapies to individuals with favourable genetic profiles. The use of such approaches may have important pharmacoeconomic benefits and lead to improved therapeutic profiles for these treatments.