Three patients had pellucid marginal corneal degeneration complicated by corneal edema. The corneal edema appeared to be a result of a break or detachment of Descemet's membrane as a result of increasing corneal ectasia. The disruption in Descemet's membrane began just above the inferior, crescent-shaped area of stromal thinning. Therapeutic modalities initially included hypertonic solution to determine whether corneal edema would resolve spontaneously, apparently by endothelial migration with healing over the break in Descemet's membrane. One patient required thermokeratoplasty and another penetrating keratoplasty for persistent stromal edema. Acute hydrops can occur with pellucid marginal corneal degeneration by a pathogenesis similar to other noninflammatory corneal thinning disorders such as keratoconus.