Depth of gastric cancer invasion is closely related to its prognosis. Details of this relationship was first reported in 1937 by juji Saeki, to whom we pay a deep respect. Exact depth diagnosis, however, is a difficult task. In our previous reports, we dealt with endoscopic diagnosis of advanced cancer simulating a superficial one. This paper is to report our study on the diagnosis of cancer infiltrating down to the muscularis propria (pm). For the past 6 years a total of 703 gastric cancers were resected in our clinics, consisting of 536 advanced and 167 superficial cancers. Of advanced cancers, pm cancers were 43 lesions accounting 8%. Twenty one cases with slight infiltration into the subserosa (ss) were added and a total of 64 lesions were analysed in this study. Spread in each layer of the gastric wall was divided into 5 degrees and the pattern of infiltration was classified into types A, B, C, and D depending on the ratio of the spread in each layer, whereas advanced cancers were divided into those simulating superficial ones and those of Borrmann's types. Type A was dominant (60%), in which ss and pm of superficial-simulating type were 30 lesions (70% of pm) and 13 lesions (60% of ss) respecively. Most of superficialsimultating type was IIc+III and Borrmann II was dominant among Borrmann's types. Endoscopic depth diagnosis was quite difficult in cases of superficial-simulating type. when the submucosal spread appeared wide, deeper infiltration was likely. On the other hand, Borrmann's type of cancer was rather easy to diagnose. It was intersting to note that pm and ss lesions were most frequently found at the 5th and 6th decades respectively. No lesions of pm and ss were found to be smaller than 1cm and 1.3cm, respectively, in maximum diameter. Some other endoscopic findings were discussed.