In this paper we have studied 649 resected cases of S0 (macroscopically negative serosal invasion) gastric cancer, this number of S0 gastric cancer resections experienced from a total number of 1692 patients treated at our hospital during the previous 16 years. The five-year survival rate of S0 cancers was 94% for patients given curative resections. Most of S0 cancers were histologically restricted within the pm layer but a few had reached the ss gamma or se layer. Non-curative factors in S0 cancers we recomposed of cancer positive stumps in the IIb-like margin, liver metastasis in the differentiated type carcinomas with ss invasion, and surgically left lymph node metastasis in the advanced carcinomas. As for lymph node dissections, our study reveals that an R2 dissection in the C and M regions, and a R3 or R2 + No.12 dissection for the A region are recommended. Modes of recurrence were characterized by liver or other hematogeneous metastasis in pm cancers or lymph node-positive cancers at the antrum, and by a peritoneal recurrence at the corpus in cases of advanced cancers. Histological ps(-) cancers showed a different survival result than did the S0 cancers and S(+) cancers.