We hypothesised that the intensity of mechanisms of glucocorticoid resistance in childhood acute lymphoblastic leukaemia might be decreased by concurrent ex vivo use of compounds with specific blocking or activating properties at different steps of the glucocorticoid intracellular pathway. The following modifiers were used: ciclosporin A, rifampicin, doxycycline, meta-iodobenzylguanidine, buthionine sulfoximine, ethacrinic acid, pentoxifylline, indomethacin, rotenone, forskolin, olomoucin, 5-aza-2'-deoxycytidine, 3-aminobenzamide, O(6)-benzylguanidine and nitroprusside sodium. All modulators sensitised lymphoblasts and potentiated prednisolone cytotoxicity in most cases indicating that various compounds, which can influence the antileukaemic effect of prednisolone during anticancer therapy, might modulate some mechanisms of glucocorticoid resistance.