Erythema multiforme is an uncommon acute inflammatory disorder caused by exposure to microbes or drugs. Erythema multiforme minor typically affects only one mucosa and can be associated with symmetrical target skin lesions on the extremities. The disease usually occurs in patients in their 3rd and 4th decade of life, but can also affect children and adolescents. Alendronate sodium has been approved for the prevention and treatment of osteoporosis in postmenopausal women, but is associated with adverse events. This study reports and discusses a case of erythema multiforme minor. In addition, a literature search of articles published in PubMed-Medline was performed. The case was a 96-year-old woman who had taken alendronate. Intraoral clinical examination demonstrated hypersalivation and macrocheilia of the lower lip, associated with an ill-defined ulcer with erythematous borders measuring 20 mm in greatest diameter and covered with serofibrinous exudates. The aging of the population in developed and developing countries has increased the use of alendronate sodium to prevent osteoporosis and clinicians should be aware of possible oral adverse events associated with this drug.