A study has been made of intraocular pressure and intraocular fluid circulation in a group of patients with unilateral retinal detachment of recent origin. The eyes without detachment were characterized by decreased intraocular pressure, outflow facility and rate of aqueous humor formation in comparison with a control group of adult subjects without ocular pathology. In the eyes with detachment, the mean intraocular pressure and mean rate of aqueous humor formation were still less than in the unaffected eyes, but the outflow facilities were approximately the same in pairs of eyes of individual patients. The results are discussed in the light of a proposal that the degenerative changes in the periphery of the retina and vitreous humor (known to be common characteristics associated with rhegmatogenous retinal detachment) and the decreased rate of aqueous humor formation indicate an underlying deficiency in the vascular circulation of the anterior uvea.