Notwithstanding the high prevalence of primary aldosteronism (PA), probably the most common form of secondary hypertension, the diagnosis of PA is often neglected or delayed, thus precluding target treatment, which is curative in many cases. For selection of the most appropriate treatment, a fundamental step is the distinction between a lateralized form, mainly aldosterone-producing adenoma (APA), and bilateral adrenocortical hyperplasia (BAH), also known as idiopathic hyperaldosteronism (IHA). To this aim all current guidelines recommend adrenal vein sampling (AVS), a technically challenging procedure that often fails, particularly in non-experienced hands. Cosyntropin (synthetic ACTH) is administered in the attempt to maximize adrenal cortisol secretion and avoid pulsatile adrenocortical hormone secretion in about 40% of the referral centres around the world. However, the Endocrine Society guidelines do not advise about the use or not of cosyntropin as stimulus during AVS, as there are arguments in favour and against its use. These arguments are presented in this debate article reflecting the views of groups that currently use and do not use cosyntropin.