The effect of the adrenal corticosteroids on intraocular pressure and fluid dynamics has been the subject of many clinical and experimental investigations. The literature in this field has been aptly reviewed in two recent publications, to which the reader is referred.1,2 The studies to be reported in this and in following publications were suggested by the finding of two patients who developed ocular hypertension during topical steroid therapy; in these cases, the hypertension could be made to disappear or reappear, respectively, with the cessation or the topical application of the synthetic analogue of hydrocortisone, dexamethasone. In so doing, these cases suggested a method of studying the effect of the steroids on intraocular pressure and its dynamics in human volunteers and patients, without the hazards and complications of systemic administration, and with the added refinement of using, as a control, the same eye or the second untreated eye of the