Individual glucocorticoid (GC) sensitivity was determined by measuring the effects of several clinically used GCs on transactivation of the GC-induced leucine zipper (GILZ) gene and on transrepression of the IL-2 gene using quantitative real-time PCR. A clear difference in relative potencies for transactivation and transrepression of the various GCs was observed, suggesting differential effects. To determine whether the in vitro outcomes could predict in vivo effects of GCs, 15 individuals underwent a 0.25-mg dexamethasone (DEX) suppression test (DST) while determining GILZ and IL-2 mRNA levels in their peripheral blood mononuclear cells incubated with hydrocortisone, DEX, budesonide, and prednisolone. No correlations were found between the DST and the two expression assays. However, significant correlations existed between hydrocortisone and DEX (r = 0.52; P = 0.046), hydrocortisone and budesonide (r = 0.48; P = 0.069), and hydrocortisone and prednisolone (r = 0.86; P = 0.007) regarding GILZ mRNA levels, and between hydrocortisone and DEX (r = 0.62; P = 0.014), hydrocortisone and budesonide (r = 0.71; P = 0.003), and hydrocortisone and prednisolone (r = 0.71; P = 0.047) regarding IL-2 mRNA levels. In conclusion, intra- and inter-individual variations in GC sensitivity were observed using two expression assays representing GC-mediated transactivation and transrepression. The two expression assays did not correlate with each other or with the results of the DST. This suggests that regulation of the hypothalamic-pituitary-adrenal axis is more complex. However, within an individual person, these two tests combined might predict what type and dosage of GC will be preferable in individual patients for its inhibitory clinical effects, together with relatively fewer transactivating effects related to adverse effects.