Of 720 patients with gastric carcinoma treated over a 6-year period, 37 (5%) were 35 years of age or younger. They differed from older patients in that the usual sex ratio was altered (18 men: 19 women), and in certain histologic features. Poorly differentiated or undifferentiated lesions predominated (34 patients), and the distribution of histologic types was unusual; two thirds each were of the diffuse type (Lauren classification) or signet ring type (World Health Organization classification), and over three quarters were infiltrative (Ming classification). Intestinal metaplasia was absent in the majority of patients, and gastritis was less commonly seen than in older patients. Although most patients had long histories of disease and advanced disease, the TNM stages and the proportion undergoing curative resection (8%) were similar to those seen in older patients. Except for one who has survived 5 years, all patients in this study have died.