As biometrics-based identity authentication systems have become more widely deployed, it has become evident that traditional identification and verification tasks are not the only application for such approaches. The prediction of individual, but non-unique, characteristics such as subject age is also an obvious option, since there are diverse situations in which information short of absolute identity is itself valuable. Physical ageing is an important issue for practical biometrics, since it is known that the associated physiological changes can impair performance for most modalities. Understanding the effects of ageing is necessary, therefore, both to optimise attainable performance but also to understand how to manage biometric templates, especially as the time elapsed between enrolment and use increases. Age prediction is relatively poorly represented in the literature. This chapter will explore applications of age prediction from iris biometrics and the implications for the underpinning computational structures.