Prehospital emergency care has developed rapidly during the past decades. The care is given in a complex context which makes prehospital care a potential high-risk activity when it comes to patient safety. Patient safety in the prehospital setting has been only sparsely investigated. The aims of the present study were 1) To investigate the incidence of adverse events (AEs) in prehospital care and 2) To investigate the factors contributing to AEs in prehospital care.