The aim of the present study was to assess the effectiveness of preemptive dexamethasone in surgery of the lower third molars and to compare it with other oral anti-inflammatories. An electronic search was conducted for preemptive effects related to lower third-molar surgery in 3 separate databases. The variables pain, swelling, and trismus were assessed. Meta-analysis was used to calculate the pooled effect measures for mean and standard deviation values (95% confidence interval [CI]). Seven split-mouth clinical trials were selected. Two studies were included in the meta-analysis. Three studies showed a low risk of bias; 2 studies exhibited a moderate risk and 2 a high risk of bias. Dexamethasone was better than nonsteroidal anti-inflammatories for preemptive effectiveness. Meta-analysis for swelling confirmed better results for dexamethasone than for methylprednisolone after 2 days (95% CI = −1.28 to −0.38), 4 days (95% CI = −1.65 to −0.71), 7 days (95% CI = −1.42 to −0.71), and overall (95% CI = −1.25 to −0.72). Dexamethasone was better than methylprednisolone for mouth opening after 4 days (95% CI = 0.18 to 1.07). There is insufficient evidence through meta-analysis to conclude that dexamethasone is better than other nonsteroidal anti-inflammatories or methylprednisolone as a preemptive analgesic. The results of this meta-analysis suggest that dexamethasone is more effective than methylprednisolone for swelling and trismus.