The effects of ethanol extract from radish seeds on gastrointestinal function in rats were investigated. Rats were divided into 2 groups of 8 rats each, the basal group and the radish seed ethanol extract group. The radish seed ethanol extract group had a significantly decreased gastrointestinal transit time, but a significantly increased fecal weight compared with the basal group. The radish seed ethanol extract group also had significantly higher duodenal villus height and greater colonic mucosal thickness than the basal group. The radish seed ethanol extract group had a greater proliferation of 5-bromo-2-deoxy-uridine (BrdU) immunoreactive cells in the gastric mucosa as well as in the mucosa and submucosa of the small and large intestine than did the basal group. Thus, radish seed ethanol extract may be useful in preventing constipation based on the observation of an increase in fecal weight, a decrease in gastrointestinal transit time, and positive changes in the intestinal mucosa.