Ninety-eight patients with suspected adrenal disease were examined by computed tomography (CT). In 73 patients adrenal disease was confirmed on biochemical and other grounds (Cushing's syndrome (38), primary aldosteronism (8), phaeochromocytoma (12), androgen excess (7), Addison's disease (1) and non-functioning adrenal masses (7)). The CT appearances of hyperplasia and benign and malignant adrenal tumours are described in detail. Ninety-six per cent of the adrenal glands were identified, and all but one of the 39 adrenal mass lesions were correctly identified and localised by CT. The failure to identify some adrenal glands and one adrenal tumour was related to a paucity of intra-abdominal fat. Two abdominal ectopic phaeochromocytoma were not identified (in one patient because the appropriate area was not scanned). The 25 patients examined with unproven adrenal disease had normal glands on CT. That some hyperplastic glands appear normal on CT precludes its use as a screening procedure for biochemically unproven adrenal disease. Computed tomography allows the differentiation of adrenal hyperplasia from functioning adrenal tumours, and the differentiation of benign from malignant lesions with a high degree of certainty; it is the method of choice for the identification and localisation of adrenal tumours.