Activated Leukocyte Cell Adhesion Molecule (ALCAM, also called CD 166, MEMD) as cell surface immunoglobulin is reported as prognostic marker in breast cancer, but its predictive value has not yet been evaluated. We have analyzed ALCAM protein expression by Western Blot analysis (n = 160) and mRNA expression by cDNA microarray analysis (n = 162) in primary mammary carcinomas. Both expression results were obtained in 133 cases, showing a strong positive correlation between protein expression and mRNA expression (P < 0.001). Neither ALCAM protein nor mRNA expression are correlated to histological type, grading, stage or age of patient. However, ALCAM protein expression correlates positively with estrogen receptor status (ER) (P = 0.025). A stratified subgroup analysis showed positive correlation of high ALCAM mRNA expression with longer overall survival (OAS; P = 0.0012) in patients treated with adjuvant chemotherapy (n = 100). In contrast, patients with high ALCAM mRNA expression who did not receive chemotherapy tended to have a worse prognosis. Similar but weaker correlations were found regarding ALCAM protein expression data. The predictive impact of ALCAM mRNA expression in chemotherapy treated patients was corroborated by multivariate Cox regression analysis also including histopathological markers (P = 0.001 for OAS). Our overall results reveal that high ALCAM expression levels in primary tumors might be a suitable marker for prediction of the response to adjuvant chemotherapy in breast cancer.