Lichen planus of the oral mucosa (OLP) is characterized by lymphocytic mucositis, basal cell lysis, and lymphocyte transmigration into the epithelial compartment. Some reports have suggested a high incidence of oral squamous cell carcinoma (OSCCA) in OLP patients and have implicated OLP as a premalignant lesion. We describe five cases of OSCCA arising in patients with preexisting OLP. At our institution, the incidence of OSCCA in patients with OLP approximates that reported in other series. The immunopathologic basis for OLP, its potential association with malignancy, and the variable clinical picture of OSCCA in patients with OLP are reviewed. Specific recommendations are given for treatment and follow-up of lesions, including the role of future testing with viral and oncogene markers.