To investigate the effectiveness of brief interventions to reduce alcohol intake in traffic casualties with a positive blood alcohol concentration. Nine hundred forty-eight eligible casualties (97.6% of eligible casualties within a universe of 1106) were screened for alcohol and 126 (13.3%) were identified as positive. Interventions were performed in 85, randomly allocated to a minimal intervention (simple advice) or a brief intervention (motivational intervention). Telephone follow-up was scheduled for months 3, 6 and 12. The present study reports the results of follow-up at month 3. Fifty-seven patients (67%) were followed up at month 3. A total of 73.7% had reduced their alcohol intake and this percentage was greater in the group who underwent the brief intervention (p = 0.06; effect size 0.5) and among heavy drinkers (p < 0.05). The data indicate the effectiveness of the brief intervention, although the sample size does not allow definitive conclusions to be drawn.