We developed a real-time RT-PCR assay for the quantification of topoisomerase II (topo II) mRNA level. It was applied on peripheral leukaemic cells from 23 patients with acute myelogenous leukaemia (AML) and 23 with chronic lymphocytic leukaemia (CLL). RNA template dilutions from 0.25 to 25ng per reaction were used as standard curves for topo IIα, β and the internal control 18S rRNA. About 57% (26/46) and 26% (12/46) of the specimens had detectable topo IIβ and α mRNA, respectively. The correlation between these two factors was ρ=0.7 and P=0.0001. No relationship between topo IIα or β mRNA level and response to chemotherapy was found in AML patients (n=19 assessable for response). Our method is rapid and convenient for quantification of topo IIα and β mRNA levels, and could be suitable for investigation in a larger population.