A 54-year-old woman presented with a unilateral, anterior uveitis that progressed to hypopyon over 4 months despite treatment with steroids. One hundred percent of the cells collected from aspirates of the anterior chamber of the affected eye were morphologically large granular lymphocytes. The aspirated cells were demonstrated by flow cytometry to be a uniform population of T lymphocytes with a diploid genome and an S fraction of 2.3%. On further investigation, the patient was found to have an extensive abdominal malignant lymphoma with the same immunophenotype but different morphologic features than the anterior chamber lymphoid infiltrate. In contrast to the cells in the anterior chamber, the abdominal tumor was highly aggressive as indicated by the cellular morphologic features and the S fraction of 43%. DNA hybridization studies of the abdominal lymphoma demonstrated a T beta 2 T-cell receptor gene rearrangement. The use of these modern diagnostic methods should facilitate the diagnosis of intraocular lymphomas and may have important therapeutic and prognostic implications in the future.