The transient receptor potential canonical (TRPC) family form a group of non-selective cation channels and are candidates for receptor-operated calcium channels (ROCs) and store-operated calcium channels (SOCs) in airway smooth muscle. TRPC1, 3, 4 and 6 have previously been shown to be expressed in cultured human airway smooth muscle (HASM) (Corteling et al. 2004) and are believed to contribute to the control of calcium homeostasis. However, little is known about how these channels are regulated and their role in disease. In this study, we investigated the regulation of TRPC mRNA expression in HASM cells by pro-inflammatory cytokines using quantitative real time PCR. Primary HASM cells were isolated from human trachea explants (with ethical approval) and cultured in vitro with cytokines: TNF-α (10ng/ml), IL-13 (50ng/ml), IL-1β (10ng/ml) and IL-4 (10ng/ml). RNA was extracted following exposure to cytokines for either 4 or 24 h and reverse transcribed to cDNA. Quantitative, real time PCR was performed on the cDNA using specific primers and probe sets designed against the different TRPC genes (TRPC1, 3, 4 and 6). An 18s ribosomal RNA specific assay was used as a housekeeping control. Relative quantitation using the comparative (Ct) method was used to analyse changes in gene expression. Expression in each of the cytokine treated samples was compared relative to the level of expression in the untreated medium controls. All experiments were performed in triplicate for each donor: HASM isolated from 3 separate donors were used. All cytokines failed to alter TRPC1, 3 and 4 expression by more than 2-fold. However, substantial changes in TRPC6 expression were observed. Incubation of HASM cells with TNF-α, IL-13, IL-1β and IL-4 for 4 h, decreased TRPC6 expression to 22±6%*, 32±12%*, 26±6%*, 53±9%*, respectively, with the medium control set to 100%. This effect was further enhanced at 24 h (4±2%*, 20±4%*, 8±3%*, 45±5%* respectively). Data are expressed as mean values ± s.e.m., n=3 donors. Comparison between groups was achieved using one-way ANOVA followed by Dunnetts multiple comparison test: *p<0.01. Cytokines such as TNF-α are thought to be important mediators of inflammatory airway disease. The current study has shown that a range of pro-inflammatory cytokines have the ability to selectively downregulate the expression of TRPC6 in HASM.