During screening for inhibitors of T cell activation, we have found that trichostatin A (TSA), known as a potent inhibitor of histone deacetylase, showed selective inhibitory activity against IL-2 gene expression. From luciferase reporter experiments on human leukemic Jurkat T cells, TSA was found to inhibit the expression of the luciferase reporter gene directed by the IL-2 enhancer and promoter with a 50% inhibitory concentration value of 0.073 μM. On the other hand, TSA, at the same concentration, enhanced the expression of the luciferase reporter gene directed by the c-fos enhancer and promoter. The result of RT-PCR experiments also indicates that TSA has selective inhibitory activity against IL-2 gene expression in Jurkat cells. These results suggest that the change in chromatin structure caused by the hyperacetylation of histone might affect the regulation of IL-2 and c-fos gene expression.