The effects of interferons (IFN)-alpha, beta 2 and -gamma in inducing megakaryocytic differentiation of blast cells from a patient with acute megakaryoblastic leukaemia (AMegL) was investigated in liquid suspension culture by the increase in CD41 and CD42b expressions using monoclonal antibodies in the APAAP technique. After six days of culture, the percentage of CD41 and CD42b positive cells increased in control cultures from 15.2% and 10.6% on day 0 to 32.0 +/- 4.3% and 22.1 +/- 2.5%, respectively. The addition of IFN-alpha significantly increased the number of CD41 and CD42b positive cells by about two to three fold compared to control cultures (p < 0.01) and by about four to six fold compared to day 0 (p < 0.001) Similarly, IFN-beta 2 induced a significant increase in CD41 and CD42b positive cells. On the other hand, IFN-gamma failed to increase the number of CD41 and CD42b positive cells in comparison to control cultures on day 6 and instead stimulated a significant increase in the number of monocytes/macrophages by about ten fold compared to control cultures in IFN-gamma-treated cultures (p < 0.001). The present results suggest that megakaryocytic differentiation of blast cells in AMegL could be induced by IFN-alpha and beta 2 and support a clinical role for them in the treatment of AMegL patients. Also, the present results showed that monocytic differentiation of blast cells in AMegL could be stimulated by IFN-gamma, supporting the multipotent stem or progenitor cell origin of the AMegL subtype of acute myelogenous leukaemia.