Several TRP channel subtypes have been found previously in airway smooth muscle. Several recent studies have found that airways respond to cold and to menthol, both of which may act through the TRPM8 channel, possibly present in epithelial cells and afferent nerve fibres (see Fischer, 2011). Our recent studies have identified that TRPM8 channels contribute to control of vascular smooth muscle tone (Johnson et al, 2009). There have been no studies as to whether this channel is present in airway tissue. Here we examined whether this channel is present in rat trachea by a combination of PCR and functional isometric tension studies. Tracheas were taken from sacrificed male Sprague-Dawley rats (250-350g). Semi-quantitative PCR was performed for TRPM8 mRNA with 3 different primers. All 3 primers were positive at the appropriate bands, both with the epithelium in tact and removed (N=1, n=3 for each primer). Isometric contraction studies were conducted in tracheal rings pre-tensed to 0.5 g with endothelium in tact. TRPM8 agonists, menthol, (300 or 600μM in ethanol; N=7, n=24), icilin (10 μM; N=3, n =10) failed to cause any contraction (where N=animals, n= preparations). Contraction (0.92 ± 0.03 g (ave.±s.e.), N=7, n=24) induced by KCl (60mM) was markedly relaxed on addition of menthol (66±1%, N=7, n=24; P<0.001, Student’s paired t-test). Ethanol alone failed to cause any relaxation to the KCL contraction (N=5, n=14). As recent studies have shown that menthol may have non-specific actions on L-type calcium channels (Baylie et al., 2010), protocols were repeated in the presence of the L-type calcium channel blocker, nifedipine (10 μM). Contraction was still present (0.64±0.02g). Menthol-induced relaxation was reduced compared with no nifedipine (P<0.001) but still present (88±2 %, N=4, n=7, P<0.01). In the presence of the TRPM8 antagonist, AMTB (20 μM), the relaxatory affect of menthol was unaffected. We conclude that menthol has a relaxatory effect in normal rat trachea that is mediated mainly by L-type calcium channels, although some of this relaxation may involve activation of TRPM8 channels.