The objective of the study was to compare the analgesic effectiveness of dexamethasone and diclofenac sodium administered preemptively after surgical removal of third molars. Forty-four ASA (American Society of Anesthesiologists) I patients (19 men, 35 women; 16–28 years old) randomly and double-blindly received diclofenac sodium (50 mg) or dexamethasone (8 mg) or placebo 1 h before surgery. Intensity of pain, measured with a visual analog scale (VAS), was the variable studied at different postoperative times (1 h, 2 h, 3 h, 6 h, 8 h, 12 h, 48 h, 4 d and 7 d). The total amount of rescue medication (TARM) ingested (paracetamol) was another variable of the study. The Kruskal-Wallis statistical test was used. A p value of < .05 was adopted to reject the null hypothesis. The dexamethasone group showed lower pain intensity (p < .05) than the diclofenac sodium and placebo groups (p < .05). No difference in TARM was observed among the groups (p < .05). Preemptively administered, dexamethasone was effective in controlling postoperative pain.