Abstract Previous studies have demonstrated that glucocorticoid resistance develops in some patients during glucocorticoid therapy due to the down-regulation of glucocorticoid receptor (GCR) expression. A new flow cytometric method has been used for monitoring the intracellular GCR level in peripheral blood mononuclear cells (PBMCs). GCR expression by different lymphocyte subpopulations (bearing surface CD4+ CD8+ or CD19+) in steroid-treated (ST) and nontreated (NT) renal transplant patients was also compared. High, decreasing-dose steroid treatment caused a reduced GCR expression in 50% of the renal transplant patients. Long-lasting, low-dose steroid therapy caused a fall in GCR level in only 11% of patients. CD4+ T lymphocytes showed both the lowest GCR level and its alteration due to steroid therapy, while CD8+ T cells and CD19+ B lymphocytes expressed higher GCR levels and were more sensitive to steroid treatment. Detection of GCR expression in lymphocytes may provide useful information about the changes of glucocorticoid senstivity during the therapy.