Purpose: To investigate prehospital peripheral venous catheters (PVCs) in relation to the frequency of thrombophlebitis. Method: Data in this prospective study were collected using three types of data source: a study-specific questionnaire, a PVC observation instrument (PVC ASSESS), and electronic patient records. The questionnaire was distributed to ambulance crews who had inserted a PVC before bringing the patient to an emergency department at a level one trauma centre in Sweden during 10 weeks in 2008-2009. Patients admitted to hospital ward were followed-up daily by registered nurses using the PVC ASSESS until the PVC was removed. Patient record data were collected by means of auditing. Results: Of the 83 patients available for follow-up, 45 (54%) developed thrombophlebitis. Quick PVC removal was performed in 32 (71%) of these patients while 13 (29%) PVCs were left in situ for 1-8 days. No association was found between the occurrence of thrombophlebitis and potential risk factors. Conclusions: Although thrombophlebitis frequently occurred in PVCs inserted in a prehospital setting, early removal of the device with complication was common. Further studies are warranted to identify the optimal in situ time for PVCs inserted by prehospital emergency teams.