In swine, as in other mammals, interferon-gamma (IFN-gamma) plays an important role in the regulation of the immune response. The objective of this work was to develop a sensitive, quantitative competitive reverse transcription-polymerase chain reaction (qcRT-PCR) assay, using an internal cRNA standard, to monitor the expression of porcine IFN-gamma gene. We applied this qcRT-PCR assay to quantify the expression of IFN-gamma transcripts in peripheral blood mononuclear cells (PBMC) incubated for different times with or without concanavalin A (ConA). Results showed that the expression of the IFN-gamma transcripts in PBMC occurred within the first 2 h after mitogenic stimulation and reached a peak after 24 h of incubation with ConA. The qcRT-PCR technique provides an efficient and sensitive tool for studying the expression of porcine IFN-gamma gene under a variety of experimental conditions. This will help to understand the regulation of T cell-mediated immune responses by IFN-gamma at the gene level.