This article describes 31 examples of acantholytic acanthoma, a newly recognized, solitary, benign cutaneous tumor. Acantholytic acanthoma was typically an asymptomatic, keratotic papule or nodule. Patients ranged in age from 32 to 87 years (median 60 years); the ratio of men to women was 2:1; the most frequent clinical diagnosis was keratosis; and half of the growths were on the trunk of the body. Histologically, the lesions showed hyperkeratosis, papillomatosis, and acanthosis. Acantholysis was an outstanding finding in all cases; the patterns resembled pemphigus vulgaris, pemphigus vegetans, superficial pemphigus, or Hailey-Hailey disease, but no patient had evidence of any of these disorders. The term acantholytic is used because acantholysis is the outstanding histologic feature in these neoplasms; acanthoma was chosen because the growths are benign tumors of epidermal keratinocytes. The relationship of acantholytic acanthoma to acantholytic blistering disease is similar to that of solitary lichen planus-like keratosis to lichen planus and epidermolytic acanthoma to bullous congenital ichthyosiform erythroderma.