Oral melanoacanthoma (OMA) is a rare benign lesion characterized by colonization of acanthotic epithelium by dendritic melanocytes. Although its pathogenenesis remains uncertain, its clinical behavior and spontaneous remission suggest a non-neoplastic nature. Clinically, it may present as a solitary or multifocal lesion; however these two variants exhibit different features. The clinical appearance of OMA is not pathognomonic and biopsy is mandatory. OMA requires no treatment or periodic observation. Here, we report a case of OMA with diffuse lesions also affecting the tongue in a 74-year-old black woman, whose diagnosis was based essentially on clinical and histological features. The immunohistochemical profile is also presented. (J Oral Sci 51, 463-466, 2009)