Frailty is one of the greatest challenges for healthcare professionals. The level of frailty depends on several interrelated factors and can change over time while different interventions seem to be able to influence the level of frailty. Therefore, an outcome instrument to measure frailty with sound clinimetric properties is needed. A systematic review on evaluative measures of frailty was performed in the databases PubMed, EMBASE, Cinahl and Cochrane. The results show numerous instruments that measure the level of frailty. This article gives a clear overview of the content of these frailty instruments and describes their clinimetric properties. Frailty instruments, however, are often developed as prognostic instruments and have also been validated as such. The clinimetric properties of these instruments as evaluative outcome measures are unclear.