For a practical need, fast and efficient methods to quantify mRNA expression are expecting. By using real-time reverse transcription polymerase chain reaction (RT-PCR) with the double-stranded DNA-binding dye SYBR Green I as a novel method, cytokine profiles (IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, IL-12p40 and IFN-γ) were analyzed in peripheral blood mononuclear cells (PBMCs) from bovine leukemia virus (BLV)-infected animals. In aleukemic cattle, IFN-γ and IL-12p40 mRNA expression was significantly increased compared to those in cattle with persistent lymphocytosis. The similar results were obtained in the case of sheep experimentally infected with BLV. Real-time quantitative PCR technique is an applicable technique for analysis of cytokine profiles in field.