Purpose The aim of this study was to identify the underlying decisions taken regarding the insertion of prehospital peripheral venous catheters in adult patients and, additionally, to ascertain peripheral venous catheter insertion rate and explore prehospital and hospital (within 24 hours of insertion) pharmaceutical treatment via peripheral venous catheters. Method This cross-sectional study gathered data through a study-specific questionnaire and patient record auditing. We distributed a study-specific questionnaire to be completed by ambulance crews, and carried out patient record auditing for 345 patients (median age 64 years, range 18–97 years) arriving at the emergency department at a Swedish level-1 trauma center in October 2008. Results Of 135 patients (39%) arriving at the emergency department with a peripheral venous catheter, 94 (70%) had received the device because the ambulance crews intended to use it for intravenous therapeutics (of which analgesics, intravenous fluids, and psycholeptics were most frequently used). In 30 patients (22%), the prehospital inserted device was not used by the ambulance crews or at hospital within 24 hours. The corresponding rate of unused peripheral venous catheters inserted in patients after arrival at the hospital was 35%. Conclusions We found that the main reason for the ambulance staff to insert a peripheral venous catheter in a prehospital setting was that they intended to use the device. Further, the rate of unused peripheral venous catheters was lower among prehospital peripheral venous catheters than hospital.