In a double-blind study, 198 patients experiencing recurrent herpes orofacialis were randomly assigned to treatment with either tromantadine hydrochloride (ViruMerz Serol, CAS 53783-83-8) or aciclovir. All patients performed an up to 5-day course of topical treatment beginning on average within 2 h after the first signs of recurrence. The herpes efflorescences and symptoms were assessed daily by the same physician for 14 days, except on weekends, and by the patients each day during the whole observation time. Rapid healing was achieved with both medications. Efficacy was assessed by rating the course of vesicle eruptions, duration until beginning of incrustation and the clinical course of the symptoms (burning, tension, pain). Equivalence between the medication groups was shown by comparative analysis of all evaluation criteria. The global efficacy and tolerability of both medications was rated by the physician as well as by the patients as good" or "very good" in more than 80% of the cases. The results of this trial show equivalence of both medications in the treatment of recurrent herpes orofacialis