ononuclear cells were isolated by centrifugation with Ficoll-Paque and cultured in RPMI 164o with or without phytohemagglutinin (PHA) for 9h at 37℃ in an atmosphere with 5% CO2. The obtained cells were incubated with anti-Fas antibody for 8h at 37℃ in an atmosphere with 5% CO2. The cells were stained with annexin V/propidium iodide and finally subjected to flow cytometry. Results: A significantly lower percentage of apoptotic lymphocytes after PHA stimulation was noted in Behcet's disease (19.7±4.1%) and VKH syn drome (2o.4±6.9%) than in controls (26.1±7.3%). The percentage of apoptotic lymphocytes without PHA stimulation also tended to be lower in the patients with BehCet's disease (12.6%) and with VKH syndrome (12.8%) than in controls (14.6%), although the difference was not significant. Conclusion: Lymphocytes in patients with either Behcet's disease or VKH syndrome are relatively resistant to apoptosis mediated by anti-Fas antibody. These apoptosis-resistant, or longlived, lymphocytes may be involved in the chronic and recurrent intraocular inflammation seen in these patients.