In order to measure muscle thickness and to define the muscular architecture at the gastroesophageal function, both en bloc fixation and a new method of preparing dried fiber specimens were used. Specimens were obtained from 32 kidney donors and human cadavers. Wall thickness was measured at 32 identical locations in the esophagus and stomach. The oblique gastroesophageal ring (GER) was the site of greatest muscular thickness and served as a reference point. From the GER the muscle thickness tapered (P less than 0.05 to P less than 0.001) in both a cephalic (esophageal) and caudal (gastric) direction for a length of 31 mm +/- 2.5 SD. The increase in thickness was due to an increase in the muscle mass (fiber aggregation) of the inner muscle coat. The muscle bundles of this coat split up 10.2 mm +/- 3.0 SD above the GER (fixed specimen) and for a length of 25 mm +/- 8 SD formed short transverse muscle clasps on the lesser curve side. Those muscle bundles on the greater curve side formed long oblique gastric fiber loops. The angle of His was inconstant in location and distal to the uppermost gastric oblique fibers (18 mm +/- 7 SD) and to the GER (9 mm +/- 6 SD).