Oral lichen planus (OLP) is a chronic disease with bandlike lymphocyte infiltration. To elucidate the immunologic phenotype of OLP, we analyzed the presence of CD5(+), CD20(+), CD27(+) and/or CD38(+) lymphocytes in a series of 70 atrophic OLP biopsy samples. CD27(+) and CD38(+) cells were present in 84% and 54% of the lesions, respectively. The lesions were graded as T-cell dominant, B-cell dominant, or a mixed lesion based on CD5(+) and CD20(+) cells in the inflammatory infiltration with the following results: 26%, 7%, and 67%, respectively. CD27 expression was found in 67% of the T-cell dominant, in 80% of the B-cell dominant, and in 91% of mixed lesions. The corresponding figures for CD38 were 72%, 80%, and 62%. CD27(+) and CD38(+) lymphocytes represent abnormal mononuclear cell populations in atrophic OLP lesions indicating 2 forms of OLP might exist with different pathogenesis, despite similar histology and clinical behavior.