Ever since its demonstration by Telesius in 1803, there have been reports on the relationship between suprarenal tumour and changes in sex characteristics and configuration.It was not, however, until the beginning of this century that a serious study of the subject began. As long ago as 1909, Bonin reported the cure of a pseudohermaphrodite by the removal of an adrenal tumour. Since that time attention has been devoted not only to tumour removal, but to surgical interference in conditions with adrenal hyperplasia. A further great impetus to clinical study has been the more recent work in the chemistry of the adrenal cortex. This has demonstrated the extraordinary ?omplexity and variety of steroids which can be isolated, and it has also been possible not only to isolate, but to assay chemically a number of the excretion products of these steroids in the urine. The earlier attempts at biological assay of these excretion products, though useful at the time as a roug,h indicator, were at best tedious and cumbersome, and in many instances misleading, as we now know that a number of such compounds are biologically inert, and many others have a reduced or modified potency.Unfortunately, the factor of adrenal tumour formation or adrenal cortical hyperplasia is common to a variety of clinical entities. This fact has led to many endeavours to formulate endocrine entities and syndrome complexes, many of which have the same apparent morbid anatomy, but vary considerably in the admixture of metabolic and sex changes which are seen clinically. In consequence, much confusion in terminology has arisen, and such terms as the adreno-genital syndrome have been used indiscriminately to cover a wide range of clinical entities.This preliminary confusion was perhaps inevitable at a time when a large amount of clinical material was under preliminary investigation, and when the only common pathological feature discernable was adrenal tumour or hyperplasia. With the advance in knowledge of the chemistry of the adrenal cortex, and the opening of opportunities for more accurate and informative data regarding the nature of the steroid excretion products, it has become of urgent and vital importance to endeavour to make the nosology of adrenal disorders more precise. Unless this can be done, and the features and, in particular, the natural history of each group can be identified with reasonable certainty, progress, not only in the further elucidation of the adrenal abnormality, but in the pharmacology and metabolism of adrenal steroids as a whole, and the assessment of the present day management and therapy of such conditions, will be indefinitely retarded.We think that one group of conditions can be sharply differentiated from the heterogenous and complex manifestations of diseases associated with adrenal hyperplasia. This condition gives rise to adrenal hyperplasia during foetal life, and the hyperplasia and excessive cortical activity continues throughout the life span. The excessive activity is localized to the elaboration of substances ...