Objective: To compare the efficacy of methylprednisolone (corticoid)versus diclofenac (nonsteroidal anti-inflammatory -NSAID-) in the treatment of inflammation and trismus after the surgical removal of lower third molars. Study design: Prospective study on 73 patients for the surgical removal of their lower third molars. These patients were separated in two groups at ramdom: the diclofenac group and the methylprednisolone group. A record card was filled in with preoperative and postoperative epidemiological and clinic data about inflammation and trismus (three facial measures and mouth opening). In order to make a broad study of data, BMDP program was used for statistics. Results: 24 hours after surgery, patients in the diclofenac group showed a more severe inflammation in one of the facial measurements (p<0.05). Trismus was very similar in both groups. Conclusions: There were no differences in trismus depending on the antiinflammatory used. Patients in the corticoid group showed less inflammation but the difference was not as important as to justify their use.