Friend murine erythroleukaemia cells (MELC) were analysed by semiquantitative RT-PCR for the constitutive and inducible expression of megakaryocyte-specific genes. Uninduced MELC expressed detectable levels of mRNAs for acethylcholinesterase (AChE), platelet factor-4 (PF4), glycoprotein IIb (GPIIb) and von Willebrand factor (VWF), whereas the erythroid α- and β-globin genes were not transcribed appreciably. However, MELC exposed to 5 mm hexamethylene bisacetamide (HMBA) or 1.5% dimethyl sulphoxide (DMSO) seemed to be channelled towards a mixed erythroid/megakaryocytic phenotype characterized by unaltered levels of VWF mRNA, increased levels of AChE, GPIIb and PF4 mRNA, and simultaneous induction of the globin genes. Megakaryocyte-related genes were expressed, in the absence of globin gene transcription, by MELC treated with either phorbol-12-myristate acetate (PMA; 100 ng/ml) or colcemid (40 nm), an antimicrotubule agent capable of promoting polyploidization in this model. Moreover, PMA and colcemid induced also de novo expression of the thrombopoietin receptor c-mpl. PMA and colcemid did not affect high basal c-myb mRNA levels which, in turn, were down-regulated upon HMBA or DMSO induction. Additionally, both uninduced and induced MELC exhibited significant levels of Epo-R and IL-3R mRNAs, whereas no expression of granulocyte/macrophage-related genes was detected. Megakaryocyte gene expression of MELC was also compared to that of other haemopoietic cell populations from normal mice and mice infected with the anaemic strain of the Friend virus. According to our results, MELC should be seen as an unique erythro-megakaryocytic model of differentiation, potentially useful for studying molecular events governing lineage commitment as well as some steps of megakaryocytopoiesis.