Abstract We have used a real-time quantitative RT-PCR technique (TaqMan, PE Biosystems) to identify genes that are differentially expressed by human polarised CD4 + T cell subsets (Th1 or Th2). The goal was to test the feasibility of the detection method in profiling the expression of a set of marker genes important for Th1 and Th2 differentiation. We demonstrate that in polarised human Th1 cells signaling lymphocytic activation molecule (SLAM), a member of the immunoglobulin superfamily, is expressed at 7–25-fold higher levels than in Th2 cells. Along with SLAM, expression of the IL-12 receptor chain β2 (IL-12Rβ2) and the IFN-γ receptor chain β (IFN-γRβ) proved to be useful molecular markers indicating the state of T cell polarisation, as previously reported. Treatment with IL-12 increased SLAM mRNA expression in T cells by 3–4-fold, whereas a number of other cytokines including PDGF-BB, IFN-αA, IFN-αA/D, IFN-β, IFN-γ or IL-9 had no effect. Stimulating T cells by co-ligating CD3 and CD28 increased SLAM protein surface expression in both Th1 and Th2 cells. In conclusion, real-time RT-PCR detection was found to be an accurate, sensitive and highly reproducible method for fast profiling of mRNA expression in Th1 and Th2 cell subsets.