Acquired melanosis is the clinical term used to describe a slowly enlarging, diffusely pigmented lesion of the conjunctiva which may also involve the lids, caruncle or cornea. The controversial histologic classifications are reviewed and suggestions made regarding useful and accurate terminology. In acquired melanosis, development of malignant melanoma may occur. Previous work indicates that the prognosis of the resulting melanoma may be assessed by histopathologic staging as is done in cutaneous melanoma. The suggested management of acquired melanosis is close observation with excisional biopsies of areas clinically suggestive of invasive melanomas. Examination of the entire biopsy by serial or staged sections is essential for accurate histopathologic diagnosis. Invasive melanomas have been conventionally treated by local excision or exenteration. Radiation therapy may be a beneficial adjunct.