A study of the ploidy patterns in gastric cancer has been conducted, focusing on 20 cases diagnosed prior to surgery as early stage gastric cancers. The gastric cancer in 10 cases was confined to the submucosa, where as in the other 10, the gastric cancer had invaded the muscle propria. The DNA ploidy patterns were classified as follows: Type D, Type A1 and Type A2. Even with gastric cancers of less than 2 cm, the likelihood that those with Type A1, and Type A2 patterns would spread into the lymph node was high (A1, 43% and A2, 67%), suggesting that careful consideration should be given to limiting the intended surgery. With gastric cancers of the Type D pattern, however, the incidence of a lymph node metastasis was low. These results are felt to be important factors when considering the extent of surgery.