The Scarff-Bloom-Richardson (SBR) grade, an important prognostic factor in breast cancer, was also associated with cell proliferation, a consistent indicator of response to chemotherapy. The determination of an association between SBR grade and responsiveness would be clinically useful. We explored the influence of SBR grade on response to neoadjuvant chemotherapy in patients with invasive ductal breast carcinoma. The present study centered on 431 patients registered onto one of four prospective phase II trials. SBR grading was performed according to the Elston method on needle core biopsies prospectively collected prior to treatment from 290 patients and on residual tumour at surgery from 171 patients. The post-operative grades were then compared with those obtained at diagnosis. Univariate and multivariate analysis were used to evaluate the significance of SBR grade on response to neoadjuvant chemotherapy. Both statistical analysis revealed that SBR grade III tumours responded better to neoadjuvant treatment than SBR grade I (p< 10-6). None of the other patient and tumour characteristics tested correlated with response. Moreover, tumour responsiveness was significantly related to changes of the SBR grade (p= 7x10-3). As a conclusion, we showed that SBR grade is a strong predictive factor of response to induction chemotherapy in breast cancer, independently of the type of regimen used. The association between evolution of the histological grade following chemotherapy and response to treatment may prove valuable for clinicians as they make their decision regarding patient therapy.