Whereas it is now more than 150 yr since T. Addison first described the clinical and pathological features of adrenal failure (1 ), the disease remains underdiagnosed, leading to unnecessary morbidity and mortality. Over the past decade, there have been important advances in elucidating the pathogeneses and underlying genetics of the individual forms of the disease. This review emphasizes the multiple etiologies and the diagnostic steps to be taken with consideration to age at onset and gender and summarizes new genetic insights in the disease.