Abstract: Actions of activators of glibenclamide sensitive K+ channels on canine colonic circular muscle were investigated. Cromakalim as well as its (‐) enantiomer lemakalim caused inhibition of spontaneous phasic contractile activity (EC50's 4.4 ± 0.1 × 10‐7 M and 2.3 ± 0.4 × 10‐7 M, respectively) and of carbachol induced activity (EC50's: 9.4 ± 5.1 × 10‐7 M and 4.3 ± 1.4 × 10‐7 M, respectively). Cromakalim and lemakalim effects were completely inhibited by glibenclamide. Additive effects between K+ channel activators and other drugs relaxing colonic muscle (the L‐type calcium channel blocker D600 and forskolin) were seen. A physiological role for specific glibenclamide sensitive K+ channels, if existing, remains unresolved. The present study indicates that the non‐adrenergic inhibitory nerves do not act through these channels, neither does stimulation of muscarinic or β‐adrenergic receptors.