A total of 2,455 conjunctival lesions in adults (over 15 years old) obtained during a 61-year period were reviewed and histopathologically classified as congenital, acquired epithelial, acquired subepithelial, pigmented, inflammatory/degenerative, and miscellaneous. The most common lesions in decreasing order of frequency were: pterygium, nevus, dysplasia, nonspecific nongranulomatous inflammation, and epithelial inclusion cyst. The most common conjunctival malignancy in adults was squamous cell carcinoma, followed by melanoma, and pagetoid change associated with sebaceous gland carcinoma. Squamous cell carcinomas arise from progressive stages of mild, moderate, and severe dysplasia. These tumors have a low malignant potential but may behave more aggressively in the spindle cell and mucoepidermoid variants. Melanomas arise de novo, from nevi or, most commonly, from acquired melanosis and have an associated 14-32% mortality rate by metastatic spread. Sebaceous carcinomas are often initially clinically misdiagnosed, involve the conjunctiva by pagetoid spread, and can have a low rate of metastasis and death if diagnosed early and excised with frozen-section monitoring of the surgical margins.