ACTH-independent macronodular adrenocortical hyperplasia (AIMAH) is rare and generally presents as a sporadic disease. We describe a familial case of AIMAH with in vivo and in vitro demonstration of aberrant 5-HT4 and vasopressin adrenal receptors. Two sisters presented with clinical and biological features of mild Cushing's syndrome with bilateral macronodular adrenal enlargement on computerized tomography (CT)-scan evaluation. In vivo pharmacological tests showed a significant increase in plasma cortisol after terlipressin and metoclopramide administration. Unilateral adrenalectomy was performed in one of these patients. Reverse transcriptase-PCR analysis of the hyperplastic tissue revealed expression of 5-HT4 receptor isoforms (a), (b), (c), (i), and (n), and of vasopressin receptors, V1 and V2. Their father and brother were overweight, had easy bruisability and presented with biological features of subclinical Cushing's syndrome. CT scan showed moderate adrenal enlargement. In vivo pharmacological screening tests for the detection of adrenal aberrant receptors in the brother were negative. Finally, three out of the two sisters' children were evaluated. They had neither clinical nor biological features of Cushing's syndrome. Their adrenal glands were normal on CT-scan evaluation. In vivo evaluation for the detection of aberrant adrenocortical receptors performed in one of these subjects was negative. In conclusion, this study shows that (i) familial AIMAH could be an autosomal dominantly inherited disorder; (ii) aberrant 5-HT4 serotonin and vasopressin receptors can be expressed in familial AIMAH; and (iii) phenotypic expression of familial AIMAH could be varied in a same family and more pronounced in female than in male patients.