BACKGROUND Constipation is a common problem in childhood, and various radiologic methods have been advocated for investigation. Colonic transit time (CTT) has been used in adults to investigate colonic motility, but few studies evaluate this method in children. Data on CTT in the normal paediatric population are scarce. METHODS The colonic transit time was measured in 22 healthy children (median age, 10 years; range, 4 to 15 years) by Abrahamsson's method. Children took bolus ingestions of radiopaque markers on 6 consecutive days, and on day 7 a single abdominal x-ray was performed. This was evaluated for total and segmental colonic transit time. RESULTS The mean total CTT was 40 hours, and the upper limit of normal (95th percentile) was 84 hours. The upper limit of normal for segmental transit time was as follows: 14 hours for the ascending, 33 hours for the transverse, 21 hours for the descending, and 41 hours for the rectosigmoid colon. CONCLUSIONS CTT provides an objective measure to assess childhood constipation. To date, 6 studies using 5 different methods have been published reporting values for healthy children. Comparing these, Abrahamson's method has low radiation exposure and is well tolerated. This study contributes additional normal values in children.