We investigated the predictive value of HER-2/neu and epidermal growth factor receptor (EGFR) in tumor tissue and prechemotherapy serum for histopathologic response in 108 patients with breast cancer undergoing neoadjuvant anthracycline-based chemotherapy. Response to chemotherapy, assessed by histopathologic classification of regression (grade 0 [no therapy effect] to 4 [no residual tumor]), correlated significantly with prechemotherapy serum HER-2/neu levels. Median prechemotherapy serum HER-2/neu levels were significantly higher in patients with regression grades 1 through 4 compared with those in patients with regression grade 0 (9.6 vs 8.55 ng/mL; P = .011; 95% confidence interval [CI], .009-.014). Median pretreatment serum HER-2/neu levels of patients with complete pathologic response (pCR) were significantly higher than in patients with moderate or no treatment response (10.95 vs 9.1 ng/mL; P = .041; 95% CI, .036-.046). Receiver operating characteristic curve analysis revealed a serum HER-2/neu value of more than 10.3 ng/mL to predict a pCR with 80% sensitivity and 69.4% specificity. There was no significant correlation of response with HER-2/neu and EGFR scores in tumor tissue or with serum EGFR levels. Results demonstrate prechemotherapy serum HER-2/neu to be a significant predictor of response to neoadjuvant anthracycline-based chemotherapy for breast cancer.