The effects of radish (Brassica oleraceae, Cruciferae) on gastrointestinal motility were examined using rat intestinal segments with myenteric plexus in-vitro and measuring the intestinal transit of charcoal in-vivo. Radish extract (10 microg mL(-1) to 2 mg mL(-1)) caused a dose-dependent increase in contractions of the duodenum, jejunum and ileum, and 1 mg mL(-1) was the maximum effective dose. The largest contraction by the extract was found in ileal segments. The extract-induced (0.5 mg mL(-1)) ileal contraction was remarkably inhibited by pretreatment of segments with atropine (10(-7) M) for 10 min, but not by hexamethonium (0.5 mM). Moreover, antagonists of the muscarinic receptor reduced the radish-induced ileal contraction by a different ratio. The rank order of inhibitory effects was 4-diphenylacetoxy-N-methyl-(2-chloroethyl)-piperidine methiodide (90.5% of control) > tropicamide (67.4%) > pirenzepine (42.8%) > methoctramine (16.7%). Oral administration of radish extract (300-500 mg kg(-1) body weight) to mice remarkably improved the intestinal transit of charcoal, and this was significantly attenuated by co-administration of atropine (50 mg kg(-1)). Taken together, these results suggest that radish extract stimulates gastrointestinal motility through activation of muscarinic pathways.