Breast helical computed tomography (CT) was evaluated for use in assessing response to neoadjuvant chemotherapy and residual tumor volume. Forty-three patients with large, inflammatory breast cancers (stage IIA, 12; IIB, 13; IIIA, 9; IIIB, 9), all histologically confirmed by core biopsy, were evaluated prior to and following neoadjuvant chemotherapy. The breast helical CT procedure involved patients in the prone position using single acquisition during quiet respiration following intravenous injection of nonionic contrast material. Helical CT results (3.2-mm slices and maximum intensity projections) were compared to clinical and mammographic evaluations, as well as to pathologic findings. All tumors were clearly visible by breast helical CT, showing important tumor enhancement. Helical CT evaluation of response to chemotherapy (using World Health Organization criteria) corresponded better with mammography (78%, Cohen's kappa statistic (kappa) = 0.65) than with clinical examination (53%, kappa = 0.30). Helical CT measurement of residual tumor volume after neoadjuvant chemotherapy and correlation with pathologic findings were globally satisfactory. The intraclass correlation coefficient was 0.69 (excellent for rounded opacities [0.97], but not as good for diffuse, scattered or multinodular opacities [0.60]). By contrast, clinical and mammographic correlations were globally unsatisfactory (0.49 and 0.28, respectively). Breast helical CT can be very useful in the quantitative assessment of response to neoadjuvant chemotherapy and preoperative determination of residual tumor volume. For this reason, it can be considered an alternative to breast magnetic resonance imaging because of its simplicity, rapidity, and accessibility.