Objective: Surgical removal of impacted mandibular third molars with primary wound closure may result in postoperative edema, facial swelling, pain, and restriction of mouth opening. The type of closure may be a cause of these complications. The aim of this study was to compare the effects of placement of a surgical tube drain before primary closure with the effects of primary closure alone after removal of fully impacted mandibular third molars. Method and materials: The study group included 13 patients aged 15 to 39 years with bilateral fully impacted mandibular third molars. The insertion of a small surgical tube drain before primary closure (drain group) was compared to a simple primary closure procedure (no drain group) after removal of the impacted third molars in a randomized crossover design. The duration of the operation was recorded. Patients were evaluated 1, 2, 3, and 7 days postoperatively for facial swelling and trismus. Results: The facial swelling experienced by the drain group was significantly less than that experienced by the no drain group. The degree of trismus was greater in the no drain group than in the drain group, but the difference was not statistically significant. Conclusion: Use of a surgical drain, especially after removal of fully impacted third molars, will reduce postoperative facial swelling.