The management and therapy of severe trauma is an important task in medicine, as trauma victims are mostly young people, and the mortality rate for severe trauma is still high. The treatment of trauma patients is cost-intensive, with an average intensive care unit stay of two weeks for survivors (ISS C 16), and sometimes an extended phase of rehabilitation. Furthermore, many resources are needed to keep an emergency medical system ready on a 24 h/7 days a week basis, including ambulance cars, helicopters, and trained personnel. Trauma centers that are properly prepared to treat severely injured patients require several structural features, including intensive care units, trauma units, diagnostic devices such as computer tomographs and a blood bank, as well as a trained team incorporating different disciplines (orthopedic and visceral surgeons, anesthesiologists, radiologists, neurosurgeons, nurses, etc.). Despite the importance of this for the patient as well as for society, there is only limited evidence for most of the diagnostic and therapeutic strategies that are applied to severely injured patients. Classical randomized trials—the best method of producing scientific evidence—are often very difficult or even impossible to perform in the setting of severe trauma care. There are many reasons for this. Patients are usually unable to provide informed consent, the time to react in a given situation is often very limited, and a large number of professionals are involved in the treatment chain from prehospital care until discharge. Therefore, other sources of scientific information, such as registries, are of high importance. Trauma registries are often found in individual trauma centers where performance and management decisions are documented internally. However, the great value of trauma registries lies in the potential to compare institutions—i.e., to compare different institutions, or to compare the same institution at different times. This of course requires structured, consistent data collection with uniform definitions. Regional and national trauma registries have created such a system, and even at the international level such activities are underway. Trauma registries in Europe have reached a consensus agreement on a core dataset for future comparative analyses [1]. A validation study just appeared in the journal Critical Care [2]. This is the first step in the direction of a joint European trauma registry. However, results from trauma registries must also be interpreted with caution. Unlike in randomized trials, the comparability of subgroups in registries cannot generally be taken for granted (this refers to comparisons between different hospitals, different diagnostic or therapeutic strategies, or time periods). Sophisticated statistical methods are needed to minimize bias and to reach a level of comparability that allows at least some major effects or trends to be identified. Such methods include subgroup analyses, parallelization, propensity score analyses, matched pair analyses, and outcome adjustment with prognostic scores. The big advantage of registries is, however, that there is hardly any limitation on sample size. Examples from existing trauma registries show that registry-based analyses are worth publishing, even in the highest-ranked medical journals [3, 4]. Finally, the quality of the results depend crucially on the quality of the data. Therefore, measures to ensure and R. Lefering (&) IFOM, Institute for Research in Operative Medicine, University of Witten/Herdecke, Cologne, Germany e-mail: rolf.lefering@uni-wh.de