We studied the esophageal transit of aqueous 99mTc-sulfur colloid in 16 normal subjects, 8 of them twice. Condensed dynamic images having a spatial and a temporal dimension fell into four patterns: (1) idealized form, (2) retrograde motion, (3) splitting of the bolus, and (4) generation of a substantial residual component. The retrograde index quantifying retrograde motion in the first swallow (RI), the rapid component mean transit time through the esophagus in the first swallow (MTT), and the residual fractions after the first, second, and fourth swallows [RF(1), RF(2), and RF(4)] were computed. The intrasubject and intersubject variation of the quantitative results suggest that normal subjects have sporadic aberrant swallows with high RI and/or RF(1). RF(2) and RF(4) showed a significant positive correlation with age.