Background and Aim: Image definition and complete small bowel examination rate are possible factors contributing to missed lesions during capsule endoscopy.This study aimed to determine the effect of coadministration of polyethylene glycol (PEG) and dai-kenchu-to (DKT) on these factors using PEG and DKT as pretreatment before capsule endoscopy. Methods: Patients who underwent capsule endoscopy at our hospital between November 2007 and August 2012 were included in the study. Patients were divided into the following three groups: those receiving no pretreatment (control, n=133), those orally administered PEG (PEG, n=20), and those orally administered PEG and DKT (15g) (PEG + DKT, n=25). Image definition and complete small bowel examination rate were examined retrospectively between the three groups. Results: Image definition in the PEG + DKT group was significantly higher than that in the control group (p<0.05), but there was no significant differences between the PEG and control groups. The complete small bowel examination rate was significantly lower in the PEG group than in the control and PEG + DKT groups (p<0.05). Conclusions: Coadministration of PEG and DKT improved image definition and prevented a reduction of the complete small bowel examination rate due to PEG in capsule endoscopy.