Recurrent oral erythema multiforme (ROEM) is an unusual subtype of erythema multiforme, which is characterized by multiple, recurrent, self-limiting, and painful oral ulcers, evidence of herpes simplex virus (HSV) infection, and absence of cutaneous lesions. The diagnosis of ROEM is difficult and challenging, because other similar diseases should be carefully excluded. Acyclovir and/or corticoids are employed but with variable results. A 52-year-old woman presented with recurrent and painful oral ulcers in the buccal mucosa, soft palate, and gingiva in the last 12 months, with 6 to 8 recurrences during this period. The histopathologic analysis revealed an unspecified chronic lymphoplasmacytic infiltrate. Serologic tests were negative, among others, for Veneral Disease Research Laboratory (VDRL) and fluorescent treponemal antibody absorption (FTA-ABS) but positive for HSV 1/2 IgG and IgM. This report emphasizes the importance of identifying the subtypes of erythema multiforme, aiming to deal with its therapeutic and prognostic implications. Recurrent oral erythema multiforme (ROEM) is an unusual subtype of erythema multiforme, which is characterized by multiple, recurrent, self-limiting, and painful oral ulcers, evidence of herpes simplex virus (HSV) infection, and absence of cutaneous lesions. The diagnosis of ROEM is difficult and challenging, because other similar diseases should be carefully excluded. Acyclovir and/or corticoids are employed but with variable results. A 52-year-old woman presented with recurrent and painful oral ulcers in the buccal mucosa, soft palate, and gingiva in the last 12 months, with 6 to 8 recurrences during this period. The histopathologic analysis revealed an unspecified chronic lymphoplasmacytic infiltrate. Serologic tests were negative, among others, for Veneral Disease Research Laboratory (VDRL) and fluorescent treponemal antibody absorption (FTA-ABS) but positive for HSV 1/2 IgG and IgM. This report emphasizes the importance of identifying the subtypes of erythema multiforme, aiming to deal with its therapeutic and prognostic implications.