This study was carried out to evaluate the compliance with a morphine protocol and its effects on pain relief in pre-hospital care. In this prospective study, pain intensity was evaluated by the Visual Analog Scale (VAS) from the beginning and every 5 min until hospital arrival (Tend). Group 1: No major deviation from the protocol (intravenous morphine as a first bolus of 0.05 mg/kg followed by repeated boluses every 5 min until VAS < or = 30 mm). Group 2: Major deviation from the protocol. There were 216 patients included. The mean dose of morphine was 9.0 +/- 5.7 mg. The morphine protocol was respected in 123 patients (57%). The mean VAS score was significantly better at Tend in Group 1 vs. Group 2 (27.8 +/- 21.1 mm vs. 37.8 +/- 22.1 mm, respectively), the degree of pain relief was significantly better (73% vs. 53%, respectively) and the initiation time for pain relief was significantly shorter in Group 1 vs. Group 2 (10 min [5-15] vs. 15 min [10-26], respectively). Satisfaction was significantly better in patients expressing pain relief than in unrelieved patients (94% vs. 61%, respectively). Out-of-hospital pain management using morphine depends on careful attention to dosage and the time interval between re-injections. Emergency teams may employ these data to improve the quality of pain relief in the field.