The aims of this study were to assess gastric emptying, small bowel transit and colonic filling in patients with motility disorders, with particular attention to the patterns of colonic filling. Gastrointestinal transit was assessed using a previously validated radiolabeled mixed meal. Fourteen patients with clinical and manometric features of chronic intestinal pseudoobstruction & classified as intestinal neuropathy and 6 as intestinal myopathy, were studied. The results were compared with those from 10 healthy controls studied similarly. Gastric emptying and small bowel transit of solids were significantly slower in both groups of patients than in healthy controls (P less than 0.05). In health, the ileocolonic transit of solid chyme was characterized by intermittent bolus transfers. The mean size of boluses transferred to the colon (expressed as a percentage of ingested radiolabel) was significantly less (P less than 0.05) in patients with intestinal myopathy (10% +/- 4% (SEM)] than in healthy controls (25% +/- 4%) or in patients with intestinal neuropathy (25% +/- 4%). The intervals between bolus transfer of solids (plateaus in the colonic filling curve) were longer (P less than 0.05) in myopathies (212 +/- 89 minutes) than in health (45 +/- 7 minutes) or neuropathies (53 +/- 11 minutes). Thus, gastric emptying and small bowel transit were delayed in small bowel neuropathies and myopathies. Bolus filling of the colon was less frequent and less effective in patients with myopathic intestinal pseudoobstruction, whereas bolus transfer was preserved in patients with neuropathic intestinal pseudoobstruction.