HER-2/neu oncogene amplification or overexpression has generated considerable interest in predicting the outcome of breast cancer in Caucasians. In the present study, Northern blot analysis was used to investigate 44 primary breast cancers of different stages in Chinese patients. Nineteen tumors (43.2%) demonstrated more than two-fold expression of HER-2/neu mRNA over adjacent non-tumor breast tissue. The incidence of HER-2/neu overexpression in this series is higher than those reported in Caucasian studies. Ethnic variation is perhaps the only contributing factor. In node-negative patients, the incidence of HER-2/neu overexpression was also higher (33.3%), which could imply a worse prognosis in node-negative Chinese patients than in their Caucasian counterparts. A significant correlation between HER-2/neu overexpression and cancer stage was demonstrated. There were also trend relationships between HER-2/neu overexpression and other prognostic factors, including the number of positive axillary lymph nodes, tumor size, hormone receptor status and age at diagnosis, but none of these correlations were statistically significant. In axillary lymph node-negative patients, HER-2/neu overexpression was associated with estrogen receptor-negative status, a factor predicting worse outcome. These findings imply that HER-2/neu overexpression may identify a subgroup of node-negative patients with a poor prognosis who would otherwise have a favorable prognosis.