In 1995, an experiment was started to give extra medical help by helicopter to patients who needed emergency treatment. The aim of the experiment was not to reduce the transportation time to the hospital, but to bring specialised medical care directly to patients as soon as possible. An evaluation study was carried out to assess the effect of the treatment given by the Helicopter Trauma Team (HTT) on survival and quality of life. The study focused on hospitalised patients suffering from polytrauma. A direct comparison between an experimental and control group was not possible, because the HTT group consisted of more severely injured patients. A refined severity index was constructed on the basis of the Revised Trauma Scale (RTS) and the Injury Severity Scale (ISS) and their sub-scores. Using this index, it was possible to make a clear distinction between three groups of patients, i.e. those with a high probability of survival (with or without special medical treatment), those with a very low probability of survival and the patients in between. It was shown that the HTT-treatment was effective. The survival rate increased for patients in the 'in between' group, but not for patients with a low probability of survival. There was no difference in the quality of life of patients from the HTT and non-HTT groups 15 months after the accident. These findings refute the hypothesis that only the most severely injured patients with a low quality of life profit from HTT-treatment.