No randomised study to date has compared the efficacy of pre- versus post-operative trastuzumab, and therefore to address this issue we present the first report of data comparing patients with HER2 positive breast cancers treated in the neoadjuvant setting where HER2 directed therapy was either commenced concomitantly with chemotherapy or in a sequential fashion following neoadjuvant chemotherapy and surgery. This evidence concerns the gene ERBB2 and breast cancer.