The steroidogenic acute regulatory protein (StAR) plays an essential role in steroidogenesis, facilitating cholesterol entry into the inner compartment of mitochondria. Mutations (either transitions or transversions) of StAR gene have been described as a cause of lethal forms of congenital lipoid adrenal hyperplasia. Adrenal incidentalomas are frequently discovered during radiologic examinations performed in patients with diagnosis for other diagnostic problems. Enzymatic defects along the steroidogenetic cascade are observed with high frequency in these patients. Aim of the present study was to asses the involvement of alteration of the StAR gene in incidentally discovered adrenal masses (incidentalomas). The mutational analysis of 32 incidentalomas demonstrated a "missense" mutation in exon five of the gene in one of the tumors analysed. This is the first evidence of an alteration of the StAR gene in adrenal incidentalomas.