Glucocorticoids continue to be the ma‐jor immunomodulatory agents used in clinical medicine today. However, their actions as anti‐inflammatory and immunosuppressive drugs are both beneficial and del‐eterious. We analyzed the effect of glucocorticoids on the gene expression profile of peripheral blood mono‐nuclear cells from healthy donors. DNA microarray analysis combined with quantitative TaqMan PCR and flow cytometry revealed that glucocorticoids induced the expression of chemokine, cytokine, and comple‐ment family members as well as of newly discovered innate immune‐related genes, including scavenger and Toll‐like receptors. In contrast, glucocorticoids re‐pressed the expression of adaptive immune‐related genes. Simultaneous inhibitory and stimulatory effects of glucocorticoids were found on inflammatory T helper subsets and apoptosis‐related gene clusters. In cells activated by T cell receptor cross‐linking, glucocor‐ticoids down‐regulated the expression of specific genes that were previously up‐regulated in resting cells, sug‐gesting a potential new mechanism by which they exert positive and negative effects. Considering the broad and continuously renewed interest in glucocorticoid therapy, the profiles we describe here will be useful in designing more specific and efficient treatment strate‐gies.— Galon, J., Franchimont, D., Hiroi, N., Frey, G., Boettner, A., Ehrhart‐Bornstein, M., O’Shea, J. J., Chrousos, G. P., Bornstein, S. R. Gene profiling reveals unknown enhancing and suppressive actions of glucocorticoids on immune cells. FASEB J. 16, 61–71 (2002)