On behalf of the local organizing committee we cordially invite you to participate in the 4th international Radboudumc Adrenal Masterclass organized by the Radboudumc Center of Expertise for Adrenal Disorders in Nijmegen, the Netherlands. The course will take place on January 24-28, 2022 in Amsterdam, the Netherlands. We aim to extend the big success of our previous masterclass in January 2019. The Radboudumc Adrenal Masterclass includes state of the art lectures and workshops on clinical and pathophysiological aspects of adrenal diseases. It serves an audience of adult and pediatric endocrinologists, clinical fellows, internists and clinical chemists who are involved in the management of patients with adrenal disease. The duration of the masterclass is 5 days, from Monday to Friday. All lectures are given in the English language. Many national and international experts contribute to an intensive program that encompasses all major adrenal disorders: hyper- and hypocortisolism, congenital adrenal hyperplasia, incidentaloma, adrenocortical cancer, pheochromocytoma/ paraganglioma and primary aldosteronism. Apart from overview lectures on theoretical and practical issues, there will be interactive sessions on patient cases with challenging diagnostic and therapeutic issues. Participants are encouraged to present their own cases. Special attention will be paid to indications and interpretation of testing, including imaging procedures. In addition, essential and practical methodological aspects of specific procedures such as adrenal venous sampling and minimally invasive adrenal surgery are demonstrated and discussed.