Retinoic acid syndrome is a serious condition that may complicate the treatment of acute promyelocytic leukaemia patients. This syndrome may be treated effectively with high-dose corticosteroid therapy and, as a result, many patients with acute promyelocytic leukaemia receive dexamethasone at some point during treatment. We investigated whether dexamethasone would also antagonize the beneficial effects of retinoic acid. In t(15;17)-positive NB4 cells, dexamethasone did not affect the retinoic acid induced differentiation, normalization of PML-nuclear bodies or the induction of thrombomodulin mRNA. Finally, dexamethasone did not inhibit the anti-proliferative effect of retinoic acid but rather showed anti-proliferative activity itself.