The purpose of the present study was to evaluate the effect of isoprenaline on gastric antral motility in conscious dogs with gastric fistula, using intraluminal strain-gauge transducers. Infusion of bethanechol increased the motility for both frequency and strength. Isoprenaline, a beta 1- and beta 2-agonist, was used alone and in conjunction with selective blockade of beta 1 and beta 2 receptors. The stimulated antral motility was dose-dependently inhibited by isoprenaline. The effect was significantly blocked by the beta 1 + beta 2-adrenoceptor blocker propranolol and by using in conjunction the beta 1-adrenoceptor blocker practolol and the beta 2-adrenoceptor blocker H 35/25. H 35/25 and particularly practolol reduced the effect of isoprenaline to some extent, but the reduction was not of statistical significance. This indicates that isoprenaline acts on antral motility through both beta 2 and beta 1 receptors. Dose-response experiments with five logarithmically increasing doses of bethanechol and one dose of isoprenaline showed inhibition of a non-competitive type.