Esophageal scintigraphy has been rather widely used, but much debated as a simple screening method of esophageal dysfunction. However, reports of normal ranges, age dependence and reproducibility are very limited. We studied 60 healthy subjects with a mean age of 43 yr (26, 19, 15 subjects aged 20-39, 40-59, and 60-79 yr) to establish normal ranges and variations of esophageal mean transit time and residual activity measured by a radionuclide method using [99mTc] pertechnetate labeled water. Mean transit time was calculated by Zierler's formula. The median values and 95% percentiles of single measurements of MTT and residual activity in the supine position were 6.1 (3.2-11.5) sec and 11.5 (3.0-50)%, respectively. The coefficients of variation (CV) were 20%-35% for mean transit time and 85%-120% for residual activity in the sitting and supine positions. When double measurements were used, the CVs were reduced to 10% for MTT and 40% for residual activity in the supine position. The values did not change with age except for a higher frequency of spikes in subjects over 40 yr. The study has demonstrated that mean transit time for radiolabeled water in the esophagus of healthy subjects, measured by double determinations, has rather low, age-independent, interobserver and intersubject variabilities. In contrast, measurements of residual activity shows unacceptably high variations.