The relations between defecographic findings, rectal emptying, and colonic transit time were analysed in 80 constipated patients (median age 49 years, range 22-87). Patients were classified into three clinically defined groups (slow transit, outlet obstruction, and a mixed group). Rectal evacuation was evaluation was evaluated by computer-based area calculation. There were no differences in defecographic findings except that evacuation was less efficient in the slow transit group compared with the mixed group (p < 0.01) and with the outlet obstruction group (P < 0.05). Transit time was prolonged in the slow transit and mixed groups compared with the outlet group (p < 0.001). Prominent impression of the puborectalis muscle during straining and the size of a rectocoele correlated with rectal emptying (p < 0.01). Perineal descent, anorectal angles, enterocoele, or intussusception were not significantly related to emptying. Prominent impression of the puborectalis muscle (p < 0.05) and impaired rectal emptying (p < 0.05) were more frequent in patients with prolonged transit time (six or more days). There was no significant correlation between transit time and rectal evacuation in the total study population. There was, however, an inverse relation between these variables (r = 0.40, p < 0.02) when all patients who claimed infrequent defecation (two or fewer/week) were analysed separately. These results did not confirm a direct relation between rectal evacuation and colonic transit time in constipated patients overall. The results are consistent with the suggestion that impaired colonic function may develop secondary to outlet obstruction in some patients.