Using agar casts of human post-mortem stomachs we have shown that (1) A 4-cm Heineke-Mikulicz (H-M) pyloroplasty increases the diameter of the narrowest area of the pylorus in every case. (2) Further increase to an 8-cm pyloroplasty leads to a further comparable increase in the size of the outlet. (3) The distortion caused by H-M pyloroplasty does not reduce the mean cross-sectioned area of the pyloric canal. (4) The narrowest area of the outlet appears to remain at the pylorus. These findings and their significance in gastric emptying are briefly discussed.