OBJECTIVE: The unpredictability of the occurrence of illnesses and injuries leading to most emergency admissions to hospital makes it impossible prospectively to collect preadmission patient-reported outcome measures (PROMs). Our aims were to review the evidence for using retrospective PROMs to determine pre-event health status and the validity of using general population norms instead of retrospective PROMs. STUDY DESIGN AND SETTING: Searches of Medline, PsycINFO, Embase, Global Health, and Health Management information. Six studies met the inclusion criteria for the first aim, and 11 studies addressed the second aim. Narrative syntheses were conducted. RESULTS: Strong associations were found between retrospective and contemporary PROMs in 21 of 30 comparisons (correlation coefficients over 0.68) and 20 of 24 showed strong agreement for continuous measures (intraclass correlations over 0.75). Categorical measures revealed only fair to moderate levels of agreement (kappa 0.3-0.6). Associations were stronger for indices than for individual items and for shorter time intervals. The direction of differences was inconsistent. Retrospective PROMs reported by elderly patients were similar to the general population but younger adults had been healthier. CONCLUSION: Retrospective collection offers a means of assessing PROMs in unexpected emergency admissions. However, further research is needed to establish the best policy for their use.