The dynamics of bile secretion was studied on 53 cannulated male Wistar rats in normal conditions and during intravenous infusions of gastrointestinal hormones. Both secretin and CCK (Boots) induced the greatest choleretic response. Bile diversion caused a significant fall in bile flow rates as compared with rats receiving constant intraduodenal infusion of Na‐taurocholate. In all the groups clear 1.5–2 hr oscillations, lasting much longer than the interdigestive motility cycles in this species, were observed. The significance of these oscillations was confirmed by the Fisher's test and the normalized periodogram values computed for the frequency band 0.2–0.33 (1.5–2.5 hr) period were significant in all the experimental groups. However, the significance of the frequency band decreased along with the increasing stimulation potency of the hormones. Thus, neither changes in bile acid secretion nor alternations in main gastrointestinal hormone levels seem to be responsible for the occurrence of the ultradian rhythm of bile flow in the rat.