Background. Our aim was to compare and assess the predictive value of CT and histopathologic grading of tumor regression at primary tumor sites in patients with squamous cell carcinoma of the oral cavity and oropharynx after neoadjuvant (preoperative) radiochemotherapy (RCT).Methods. We investigated 55 patients with carcinomas of the oral cavity and oropharynx who underwent RCT before curative surgery. Two blinded observers measured RCT-induced reduction of tumor volume in pretherapeutic and posttherapeutic CT scans. Volume changes were compared with histopathologic findings obtained at surgery.Results. Histopathologic response evaluation revealed 31 complete remissions, 12 cases of partial response, and 12 nonresponders. We performed a logistic regression analysis to evaluate whether measured volume reduction could predict the