The effect of age on the prognosis of breast cancer remains controversial. To investigate the role of age, we reviewed 316 patients with stage I or II breast cancer. There were 14 patients below 34, 146 between 35 and 49, 115 between 50 and 65, and 41 over 66 years of age. No correlations were observed between age and clinicopathological variables. Breast cancer patients aged 34 or less had a significantly worse survival compared to those in the older age groups. Multivariate analysis also showed younger age to be a significant factor, followed by lymph node status. Therefore, younger age at onset is considered to be an independent prognostic factor.