BACKGROUND: The Mobile Emergency Care Unit in Odense, Denmark consists of a rapid response car, manned with an anaesthesiologist and an emergency medical technician. Eleven per cent of the patients are released at the scene following treatment. The aim of the study was to investigate which diagnoses were assigned to patients released at the scene following treatment, to investigate the need for secondary contact with the hospital and to assess mortality in patients released at the scene. METHODS: All records regarding patients released at the scene from 1 January 2008 to 31 December 2010 were investigated. In each patient, diagnosis as well as any renewed contact with the Mobile Emergency Care Unit or the hospital within 24 h was registered. RESULTS: ONE THOUSAND SIX HUNDRED NINE: patients were released at the scene. Diagnoses within the category 'examination and investigation' [International Classification of Diseases 10th revision (ICD-10) chapter XXI] represented the largest group of patients (28%). Diseases not elsewhere classified (ICD-10 chapter XVIII) including 'syncope and collapse' represented the second largest group of patients (24%). One hundred thirteen (7%) had a renewed contact with the Mobile Emergency Care Unit within 24 h. Of the 143 victims of traffic accidents, 19 (13%) required renewed contact with the emergency department and one required admission to hospital (0.7%). Of all 1609 patients, four died within 24 h of contact (0.2%). CONCLUSION: Patients treated and released at the scene presented poorly defined conditions. Ninety-three per cent of all cases required no secondary contacts with the health care system. However, caution should be exercised when releasing patients at the scene following traffic accidents.