The effect of the K(+)-channel opener cromakalim (BRL 34915) on the electrical and contractile activity of the smooth muscle of the cat gastric antrum has been studied. Cromakalim induced a concentration-dependent inhibition of the contractions and shortening of the sustained partial repolarization phase of the plateau action potential. High concentrations of cromakalim produced hyperpolarization and shortening of the repolarization and depolarization phases of the plateau action potential. The K(+)-channel blockers 4-aminopyridine (10(-2) M) and tetraethylammonium (10(-2) M) decreased the effect of cromakalim on the phasic contractions, while glibenclamide (5 x 10(-5) M) completely abolished it. We suggested that the inhibitory effect of cromakalim on the electrical and contractile activity of the gastric antrum smooth muscle is due to the cromakalim-induced increase of the outward K(+)-current through glibenclamide-dependent K(+)-channels.