Aim — to compare diagnostic significance of daily pH-grams of the esophagus (DeMeester score, % of time with pH 0.8—4.0) and three acidity indicators considering mean concentrations of positive hydrogen ions in daily pH-grams proposed by the staff of «Istok-Sistema» Closed Joint-Stock Company. Material and methods. There were 94 patients with pathological (over 14,72) and normal (less than 14,72) DeMeester score. The results of daily pH-grams of the esophagus were assessed by using of acidity indicators (median pH, mean square pH, average pH, percentage of time with pH <4, acidity index, DeMeester score) and new variables of pH-grams of the esophagus based on mean concentration of positive hydrogen ions. Three indicators were proposed to assess the acidity of esophagus: 1) mean pH based on average concentration of positive hydrogen ions of the entire pH-gram of the esophagus; 2) overall time with pH 0.8—4.0 equal to the sum of the products of the percent of time of acidic GERs with pH<4 in the intervals: 0.8≤pH<1.0; 1.0≤pH<2.0; 2.0≤pH<3.0; 3.0≤pH<4.0 and the coefficients taking into account the actual average acidity in certain intervals of the daily pH-gram of the esophagus; 3) pH of the esophagus as equal to the sum of the products of mean daily concentrations of H+ ions (mmol/l) and durations (in hours) of the impact on the mucous membrane of the esophagus in the intervals 0.8≤pH<1,0; 1,0≤pH<2,0; 2,0≤pH<3,0; 3,0≤pH<4,0. Results. It was found that the use of three proposed acidity parameters provides a higher accuracy in calculation of normal and pathological GER in the esophagus compared with DeMeester score and percentage of time with pH <4 in the range of 0.8≤pH<4.0. Conclusion. Assessment of DeMeester score, percentage of time with pH <4 in the range of 0.8≤pH<4.0, median pH, mean square pH, arithmetic mean pH can lead to the errors in evaluation of the results of daily pH-metry. It is advisable to apply above-mentioned values considering mean concentration of positive hydrogen ions in the stomach and esophagus in order to obtain the correct acidity values. This will significantly reduce the likelihood of errors associated with the influence of food intake, duodenogastric reflux (DGR) and other factors on the average daily pH.