PURPOSE: We have assessed the clinical usefulness of solid maker transit technique and Barr-score in 31 patients with idiopathic constipation (male:female; 17:14, mean age; 6.7 years, range 1.4-12 years). METHODS: All patients underwent full history taking and physical examination including rectal examination. On first visit to gastroenterology clinic a plain abdominal film was taken for Barr-score which evaluated by two observers without the information of the patients. Kappa score was calculated for inter or intra observer variability. Sitz marker were given orally at 9 am on days 1, 2 and 3, and another plain abdominal film was taken on day 5. Total remained solid marker were counted for the degree of retention. We calulated the residual sitz marker. Each film was divided into right colon, left colon and rectosigmoid areas, using bony landmarks, and the marker content of each area counted. RESULTS: 2 patients were excluded because they resisted to take sitz maker. Transit times were normal, mild, moderate and severe delay in 12 patients, 2 patients, 3 patients and 12 patients respectively on day 5 film. The correlation coefficiency between the degree of transit delay and clinical severity was 0.89. Among 14 patients with transit delay, 12 patients has outlet obstruction, 1 patient right colonic delay and 1 patients left colonic delay. The Kappa for inter and intra-personal variability were 4.13 and 4.18 respectively (moderate consistency each). The correlation coefficiency between Barr-score and solid marker colonic transit time was 0.603 (P=0.0008). CONCLUSIONS: This results showed that the solid marker colonic transit time and Barr score were useful in evaluation of patients with constipation.