Background: Evidence maps build on systematic review methods to find, review and organise research evidence in a broad clinical area. The Global Evidence Mapping (GEM) Initiative has developed evidencemaps for traumatic brain injury (TBI) and spinal cord injury (SCI) in prehospital, acute and rehabilitation and long-term care settings. Methods: Development of the evidence maps involved four steps: question development, prioritisation, searches and data extraction. Question development involved four data collection exercises: consultation with experts, a preliminary literature search, mapping workshops and a survey. The data from these exercises was coded and answerable clinical questions generated for each of the identified codes. The questions were prioritised using an online survey. Searches were run in seven English, four non-English and two clinical trials databases. Citations were reviewed against a priori inclusion criteria first by title and abstract and then in full-text. Data were extracted on the number of relevant studies and the design of each included study. Results: One hundred and twenty-nine questions were generated. Sixty of these questions were prioritised and evidence maps have been completed for 53 of these questions. Several evidence gaps were identified. For ten of the 53 mapped questions (19%) the evidence maps did not identify any relevant primary comparative research studies. For twelve of the 53 priority questions (23%) we found more than one comparative primary study, but no systematic review. For the remaining 31 of the 53 prioritised questions (58%) there is either a systematic review, or only one comparative study has been conducted. Conclusions: The GEM Initiative evidence maps can help researchers and research funding bodies to target areas where primary research and systematic reviews are needed to answer questions of clinical importance, and help clinicians, policymakers, patients and carers determine where evidence is available to guide healthcare decisions.