Sixty patients with anterior mediastinal neoplasms undergoing computed tomography before surgical exploration were entered in a prospective study to assess the value of computed tomography in the preoperative staging of anterior mediastinal tumours. Correct prediction of location, size, and tissue density was obtained in all 60 cases. Correct identification of the nature of the tumours was achieved by computed tomography in 37 of the 54 previously undiagnosed cases. Particular attention was given to the evaluation of the relation of the tumour to adjacent mediastinal structures, to predict the feasibility of radical surgical procedures. Overall sensitivity, specificity, and accuracy in identifying resectability were 46%, 85%, and 64%, with positive and negative predictive indices of 78% and 58%. Capsulated or highly invasive lesions were clearly distinguished, and the presence or absence of infiltration of mediastinal vessels, pericardium, and chest wall was correctly recognised in most cases. It is suggested that the evaluation of anterior mediastinal neoplasms should include computed tomography because of its accuracy in predicting size, location, and tissue density of the neoplasm. Computed tomography may suggest, often with good reliability, the histological type of the tumour and its relation to contiguous mediastinal structures, thus contributing to the choice of the appropriate surgical approach or route for biopsy.