The intravitreal injection of steroids may be potentially useful in the treatment of endophthalmitis and other ocular inflammatory diseases. The retinal toxicity and intraocular turnover of aqueous solutions of dexamethasone sodium phosphate in doses ranging from 440 to 4000 micrograms were evaluated in the rabbit; evaluation was also performed for a 0.1-mL injection of a commercially available preparation (dexamethasone phosphate [Decadron] injection, 4 mg/mL). After the 440-micrograms dose, a transient increase in staining of the Müller cells was observed, which normalized after 2 days. Progressively higher doses resulted in an increasing spectrum of disorganization in Müller and other retinal cells. The half-life of the intravitreally injected drug was 3.48 hours. These findings suggest a primary interference in Müller cell function, possibly through dexamethasone-induced alterations in retinal glutamate or glucose metabolism.