Adrenal tumours had been discovered incidentally (since 1981) in 32 patients (23 females and nine males; mean age 54 [25-73] years) who had had computed tomography (CT) or ultrasonography for other reasons: none had a history or symptoms of such tumour. Tumours were bilateral in eight, right or left-sided in 12 each: all had been confirmed by CT. Average tumour size was 3 cm (1-9 cm). Three patients had cortisol-producing adrenal tumours, and there was one benign phaeochromocytoma (abnormally high adrenaline and noradrenaline excretion). Fine-needle biopsies in two patients revealed a benign histology. An adrenalectomy was performed in eight patients (the one phaeochromocytoma, six adenomas and one ganglioneuroma). Follow-up CT in 11 of the non-operated patients 6-48 months later (mean of 14 months) did not demonstrate any increase in tumour size so that a waiting attitude seems justified: benign tumours are clearly much more frequent than malignant ones. However, if the tumour diameter is greater than 6 cm, an adrenalectomy is indicated because of the danger of malignancy.