To develop a 13C-urea-containing capsule for more economic and sensitive diagnosis of Helicobacter pylori infection, the 13C-urea-containing capsules were prepared with various additives such as polyethylene glycol, microcrystalline cellulose, sodium lauryl sulfate and citric acid. Their dissolution test and 13C-urea Breath Test in human volunteers were then performed. Polyethylene glycol increased the initial dissolution rates of urea and difference delta 13C values from 13C-urea, while microcrystalline cellulose and sodium lauryl sulfate decreased them. Irrespective of addition of citric acid, the compositions with polyethylene glycol showed higher values from 13C-urea compared to a commercial 76 mg 13C-urea-containing capsule due to higher initial dissolution rate. The capsules with 38 mg 13C-urea and 1.9 mg polyethylene glycol, which showed higher Helicobacter pylori-positive value of about 8 per thousand at 10 min, improved the sensitivity of 13C-urea in human volunteers. Thus, the 13C-urea-containing capsule with polyethylene glycol would be a more economical and sensitive preparation for diagnosis of Helicobacter pylori infection.