Criteria for the Callender classification of uveal melanoma are subjective and lead to variations among observers of the same tumor. Two other measures for cell type-the number of epithelioid cells per high-power field (Epi/HPF) and the inverse SD of nucleolar area (ISDNA)-were evaluated as prognostic factors for survival following enucleation for uveal melanoma in 232 patients. Variables significantly related to the number of Epi/HPF were related to ISDNA. Larger, more anteriorly located tumors had a high number of Epi/HPF and a low ISDNA. The two measures were also correlated. Using Kaplan-Meier survival analysis, both measures were related to tumor deaths. Worse prognosis was associated with a higher number of Epi/HPF and a lower ISDNA. Considered together in Cox' proportional hazards analysis, both measures independently predicted outcome. Separately, each measure predicted uveal melanoma-related deaths, in combination with largest tumor dimension, invasion of tumor to the line of transection, and location of the anterior tumor margin. Although ISDNA is the more objective measure of cell type, its practicality compared with other measures of cell type must also be considered.