AIM: To compare the effect of oral erythromycin vs no preparation with prokinetics on the transit time and the image quality of capsule endoscopy (CE) in evaluating small bowel (SB) pathology.METHODS: We conducted a retrospective, blinded (to the type of preparation) review of 100 CE studies,50 with no preparation with prokinetics from one medical center (Group A) and 50 from another center with administration of a single dose of 200 mg oral erythromycin 1 h prior to CE (Group B).Gastric, SB and total transit times were calculated, the presence of bile in the duodenum was scored, as was cleanliness within the proximal, middle and distal intestine.RESULTS: The erythromycin group had a slightly shorter gastric transit time (21 rain vs 28 min, with no statistical significance).SB transit time was similar for both groups (all P > 0.05).Total transit time was almost identical in both groups.The rate of incomplete examination was 16% for Group A and 10% for Group B (P = 0.37).Bile and cleanliness scores in different parts of the intestine were similar for the two groups (P > 0.05).CONCLUSION: Preparation for capsule endoscopy with erythromycin does not affect SB or total transit time.It tends to reduce gastric transit time, but it does not increase the cecum-reaching rate.Erythromycin does not adversely affect image quality.We consider the routine use of oral erythromycin preparation as being unjustified,although it might be considered in patients with known prolonged gastric emptying time.