In some patients receiving corticotropin there develops an eruption which, in many respects, resembles acne vulgaris. Certain clinical features (Table 1) distinguish the drug eruption (Fig. 1) from acne vulgaris. The purpose of this report is to compare the histopathologic features of the two conditions. MATERIAL Biopsy specimens were taken from early and advanced lesions of 6 patients exhibiting acneform eruptions due to corticotropin and from similar lesions of 15 patients with acne vulgaris. The clinical features of the two groups are summarized in Tables 2 and 3. RESULTS A comparison of the microscopic findings is listed in Table 4. In summary, there are similarities in the development of the two