To report the use of perfluoropropane (C3F8) gas in the repair of Descemet's membrane detachments. Descemet's membrane detachments after cataract surgery in three eyes and pars plana vitrectomy in a fourth underwent anterior-chamber gas-exchange descemetopexy with an isoexpansile 14% mixture of C3F8 to facilitate reattachment of Descemet's membrane. Descemet's membrane detachment was successfully reattached after anterior-chamber gas exchange with 14% C3F8 in three of the four eyes treated. The fourth eye treated with 14% C3F8 probably failed Descemet's membrane reattachment because of an unrecognized viscoelastic bleb situated anterior to Descemet's membrane. No corneal decompensation or fluctuations in intraocular pressure were believed to be attributable to isoexpansile C3F8 gas exchange. Early recognition and repair of Descemet's membrane detachments may prevent complications, such as corneal decompensation, corneal opacities and edema, and an overall decline in visual acuity. Isoexpansile C3F8 is demonstrated as a safe and efficacious alternative for the repair of Descemet's membrane detachment.