We studied c-erbB-2, p53, and nm23 gene products in 112 primary breast carcinomas. Fifty patients were aged 35 years or younger, and 62 were aged 36 to 50. Clinicopathological criteria including clinical stage, hormone receptor status, histological types, histological grades, and lymph node status, were reviewed. Disease-free survival (DFS) and overall survival (OS) were analyzed. Immunohistochemical findings were assessed semiquantitatively. Correlation between clinicopathological criteria, survival data, and immunohistochemical findings have been made. Patients aged younger than 35 years with stage I to II disease had a shorter DFS (P = .03) than older patients. However, no other clinicopathological finding was associated with age. Neither was there association between age and c-erbB-2, p53, or nm23 patterns of expression. p53 positivity was associated with high histological grade (P = .003) and with progesterone receptor negativity (P = .045). Nm23 nuclear positivity was associated with early clinical stages (P = .011) and with absence of axillary lymph node metastasis (P = .007). p53 and c-erbB-2 overexpression were associated with shorter OS while nm23 nuclear positivity was associated with longer OS in univariate and multivariate analyses. Univariate analyses showed that c-erbB-2 or nm23 were potentially important prognostic factors in women aged 35 years or younger while p53 was associated with prognosis in women aged 36 to 50. Cox model analysis indicated that c-erbB-2 alone was associated with prognosis in women 35 years and younger, whereas p53 alone was associated with prognosis in 36- to 50-year-old women. These results suggest that breast cancer in the youngest women has some biological specificity.