We studied in the rabbit the effects of pharmacologic agents on the absorption of Hanks' solution from the subretinal space of experimental nonrhegmatogenous detachments. Intravenous acetazolamide had no effect at a clinical dose (15 mg/kg) but increased the rate of fluid absorption significantly at high doses (50 mg/kg). Acetazolamide causes systemic pH to fall, while PCO2 and PO2 increase; however, duplicating some of these effects by artificial respiration or breathing 95% O2 plus 5% CO2 did not alter the rate of fluid absorption. Adding cyclic AMP and related agents to the vitreous and subretinal space slowed down fluid absorption by 25%, whereas cyclic GMP analogues increased the rate of absorption by 33%.