Conjunctival squamous cell carcinoma (SCC) can develop from carcinoma in situ or severe dysplasia known as conjunctival intraepithelial neoplasia (CIN). Conjunctival intraepithelial neoplasia and SCC are histopathologically well-defined conditions. However, it is difficult to determine the grading of dysplasia by clinical morphologic findings. Recently, proliferating cell nuclear antigen (PCNA) immunostaining, p53 immunostaining, and argyrophilic nucleolar organizer regions (AgNORs) staining have been established as valuable means of studying the biologic behavior of malignant cells. In the present study, these three staining techniques were used to examine histologic preparations of three conjunctival dysplasia and one SCC lesion. Five conjunctival tumor samples were obtained from four patients between July 1993 and October 1995. Following formalin fixation and embedding in paraffin, PCNA, and p53 immunostaining and AgNORs staining was performed with all tissue specimens. The PCNA-positive rate was the highest in SCC, followed by severe dysplasia and mild dysplasia. The p53-positive rate was the highest in severe dysplasia, followed by mild dysplasia, and negative in SCC. The AgNORs-count increased as malignancy advanced. These staining methods, which are markers for proliferative potency and cell differentiation, will be useful for early detection of changes in malignancy and will aid in decisions on treatment and prognosis.