OBJECTIVE To test the effectiveness of lag screw fixation in their application in the treatment of mandibular fractures. METHODS Sixty-nine mandibular fractures in 30 patients treated with lag screws were evaluated retrospectively regarding the cause, the type, and the site of fracture as well as the local situation and the complications encountered. RESULTS In 19 fractures a neutralization plate was used and in another 17 the lag screw was applied in combination with a compression plate. In 33 cases at least 3 lag screws were inserted. Seventy-five percent of the cases were in patients between 10 and 39 years old; 70% were the result of road traffic accidents. Most patients presented two mandibular fractures; the symphyseal area were most frequently affected. Teeth in the line of fracture were not removed, and no drains were used. Complications included two minor malocclusions, one delayed union, two cases of temporary paresis, two cases of transient hypesthesia, two cases of scar formation on the incision line, and a case of temporary trismus. CONCLUSIONS Approximately 30% of the patients treated with lag screws according to the methods outlined in this study developed complications that were either minor, transient, or both; some were related to the approach rather than the method. The most frequent complications were minor malocclusions, transient facial paralysis, hypoesthesia, and scar formation.