The trophic influence of gastrin on cellular proliferation in rodent gut has been described. Proglumide, a specific competitive inhibitor of gastrin, can exert an antitrophic effect and can block pentagastrin‐stimulated DNA synthesis. We performed this study in order to determine whether the circadian system influenced the interaction of endogenous gastrin and exogenous proglumide on DNA synthesis in several organs in 154 CD2F1mice. The mice had been acclimated to a light‐dark cycle on 12:12 before the study was begun. One‐half of the mice received intraperitoneal injections of proglumide every 8 h for 2 days (6 doses, 250 mg/kg): controls received saline injections. Beginning 8 h after the last dose, mice were killed by cervical dislocation every 3 h for 30 h. Incorporation of tritiated thymidine (DNA synthesis) was measured in the esophagus, the glandular and nonglandular stomach, spleen, and proximal and distal colon. In every organ, significant circadian rhythms were found (p < 0.01). Cosinor analysis for each organ described no significant differences in mesor, amplitude, or acrophase between the two groups, except in the glandular stomach. When circadian rhythmicity was considered, proglumide did not appear to alter DNA synthesis in the mouse gut, except to increase the overall activity in the glandular stomach. This finding differs with published reports that proglumide is antitrophic.