PURPOSE: The relationship of the age at diagnosis and the prognosis in breast carcinoma remains controversial. However, it is a widely held belief that breast cancer in young women especially women in the twenties is a disease more lethal than that found in older patients. We attempted to determine whether young age could be a poor prognostic factor for breast cancer. METHODS: A retrospective study was conducted of all women age 30 or younger who had undergone a definite operation from September 1994 to December 1999 in the Department of Surgery, Samsung Medical Center. Clinical features, histopathologic findings, and prognostic factors were evaluated and compared with those for the older group. RESULTS: There were 30 cases (75%) of infiltrating ductal carcinomas in the twenties, which was relatively less than that in the older group (84.8%)(p=0.001). Ductal carcinomas in situ and special types such as mucinous, secretory, and medullary carcinomas and phyllodes tumors were noted more and infiltrating lobular carcinomas less in the younger group than in the older group. Patients in the twenties had smaller tumors (p=0.001) and fewer axillary lymph node metastases (p=0.018) than those in the older group. There were no significant differences between the groups of age 30 or younger and older in terms of the extensive intraductal component (EIC), histologic and nuclear grades, hormonal receptors, p53 mutation rates, and TNM staging (p>0.05). The Nottingham Prognostic Index used to assess the prognosis in breast cancer patients failed to prove the young age as a poor prognostic factor (p=0.133). CONCLUSION: Breast cancer in our study population of women in the twenties did not have a poor prognostic factor. We conclude that age itself is not a poor prognostic factor in patients with breast cancer.