Epithelial renewal of the small intestine was measured in the Syrian hamster utilizing tritiated thymidine by standard autoradiographic and a scintillation counting technique. Scintillation counting of intestinal replicates proved to be as accurate as standard autoradiography. Average mucosal cell turnover was 71 +/- 3.0 hr in jejunum and 79 +/- 4.2 hr in ileum. Scintillation counting was utilized to study the effect of a maximum cholera enterotoxic secretory stimulus on small intestinal mucosal cell turnover. No significant change in epithelial cell migration occurred during cholera enterotoxin (CT)-induced fluid and electrolyte secretion. The rate of decline in radioactivity as a measure of cell turnover in CT-exposed animals was no different from controls. Epithelial cell proliferation 1 to 42 hr after CT exposure showed no difference from controls. Intestinal fluid and electrolyte secretion persisted for 24 hr after CT exposure. It is concluded that (1) the small intestinal epithelial cell migration was unaltered by this metabolic secretory stimulus, and (2) the data are consistent with the concept that epithelial migration after CT exposure was one factor, although not necessarily the major determinant of the progressive decline in intestinal secretory activity.