Computed tomography (CT) and conventional chest radiography were reviewed in retrospect in 84 patients in whom pleural pathology was suggested clinically. The importance of administration of contrast medium in distinguishing between malignant lesions and other pleural diseases was given special attention. CT was found to be of value in diagnosing and establishing the extent of pleural lesions, especially in the mediastinal region. All malignancies exhibited high contrast enhancement following intravenous bolus injection of contrast medium. There were no features specific for mesotheliomas distinguishing these from other pleural malignancies. Some benign infectious lesions also showed high contrast enhancement. High contrast enhancement thus indicated malignancy only if an infectious lesion could be excluded. If contrast enhancement was absent or slight, the lesion was likely to be benign. Clinical follow-up may be regarded as justified in such cases. Indirect signs were not helpful in distinguishing between malignant and benign lesions.