Respiration hydrogen analyzer H2Rate has been used in pilot examinations of a group of students. This method for noninvasive diagnosis of small intestinal diseases promotes proper interpretation of the results. Free hydrogen level in the exhaled air increases as a result of lactulose (diagnostic agent) cleavage by enteric microflora within about 3 h. Based on the experimental data, the main groups with characteristic curves reflecting the time course of hydrogen concentrations have been distinguished. Excessive bacterial colonization of the intestine can correspond to emergence of characteristic peaks of hydrogen concentrations in the curve. Hydrogen concentrations in exhaled air can also be analyzed to evaluate the rate of the substrate propulsion in the middle compartment of the intestine.