Repeatable measures are essential for clinicians and researchers alike. Both need baseline measures that are reliable, as intervention effects cannot be accurately identified without consistent measures. The intrarater and interrater reliability of the new Foot Posture Index and current podiatric measures of foot position were assessed using a same-subject, repeated-measures study design across three age groups. The Foot Posture Index total score showed moderate reliability overall, demonstrating better reliability than most other current measures, although navicular height (normalized for foot length) was the single most reliable measure in adults. None of the tested measures exhibited adequate reliability in young children, and, with less-than-desirable reliability being demonstrated, most measures need to be interpreted accordingly when repeated measures are involved.