OBJECTIVES: To assess the usefulness of adrenal scintigraphy for clinical evaluation of adrenal incidentalomas, and its relation with pathological diagnosis and follow-up. PATIENTS AND METHODS: We have studied 46 patients with unilateral adrenal incidentaloma of size between 10 and 100 mm (average 30.5 +/- 19 mm). The lesions were discovered with abdominal computerized tomography in the study of a primary tumor (22%) or in the evaluation of benign pathology (78%). Adrenal scintigraphy assessed uptake in adrenal incidentaloma. Hormonal study included urinary catecholamines, plasma cortisol after dexamethasone, adrenal androgens, and renin and aldosterone in hypertensive patients. Five patients were operated, FNAB was carried out in three patients, and in the rest average follow-up was 29 +/- 21 months. Adrenal incidentaloma was considered nonfunctional if the lesion did not modified its size nor showed analytical alterations along a follow-up higher than 8 months. RESULTS: Of 46 adrenal lesions, seven didn't show uptake (three metastases, one cyst, one adrenal carcinoma, one pheochromocytoma, and one angiomyolipoma), 34 showed excessive uptake (29 nonfunctional adrenal nodules and 5 hyperfunctional adrenal nodules), and five had normal uptake (nonfunctional adrenal nodules). Adrenal scintigraphy was compatible in all cases with cytological study or the response to chemotherapy. Along the follow-up, growth of the lesion was demonstrated in 23%, and reduction or disappearance of the lesion in 11%, with no hormonal significant changes. CONCLUSIONS: Detection of a lesion with no uptake in adrenal scintigraphy forces to carry out complementary explorations in order to rule out malignant pathology. A lesion with excessive uptake is indicative of a benign process and should be assessed with hormonal determinations.