When performing extensive resections for carcinoma of the stomach, one of the most important considerations is to resect clear of the growth. In this paper it is proposed to show how a general estimate can be made of the probable extension of any given carcinoma into and through the gastric wall. The problem must have presented itself first to Billroth, the originator of resection of the stomach, for Guinard1 quoted von Eiselsberg as saying that in Billroth's clinic the resected portion extended several centimeters beyond the growth. Mikulicz2 advocated removal of from 5 to 10 mm. of duodenum and from 5 to 10 cm. of apparently healthy stomach, but in a well defined tumor he thought that removal of from 1 to 2 cm. of apparently healthy stomach was sufficient. Czerny3 was more moderate, and advocated removal of 3 cm. of apparently healthy tissue. Guinard himself thought