To investigate using immunohistochemistry the unusual finding that tumor infiltrating lymphocytes (TIL) in uveal melanomas are associated with a higher mortality rate. We performed immunohistochemistry for B and T lymphocytes on 80 uveal malignant melanomas, which previously had been reported to contain more than 100 TIL per 20 high-powered fields. In a second study of 90 patients, we counted the number of immunohistochemically stained T lymphocytes per 20 high-powered fields in uveal melanomas from 30 patients who survived at least 15 years after enucleation, from 30 patients who died with metastasis within 2 years, and from 30 patients who died with metastasis more than 10 years after enucleation. T cells predominated in 73.8% of the 80 patients, and B cells were more prevalent in 13.8%. T cells were usually scattered, and B cells were usually in clumps. Post-enucleation 18-yr mortality from metastasis was 73% for patients with either T-or B-cell predominance of their TIL. The mortality rate was 32% for patients with few TIL. The patients who survived at least 15 yrs after enucleation had fewer T lymphocytes infiltrating their uveal melanomas than the two groups of patients who died with metastasis. The pattern of the TIL was different for T and B cells in uveal melanomas. T-lymphocytic infiltration is associated with death due to metastasis.