The purpose of this study was to evaluate the efficacy and safety of biodegradable intrascleral implants for the slow release of triamcinolone acetonide (TA). Intrascleral implant (1 mm thick; 3 mm diameter) was made of PLA (poly(D,L-lactide)) containing 6.4 mg of TA with one-side coating of high molecular weight PLA to render unidirectional drug absorption through the sclera. In vitro TA release was evaluated by liquid chromatography-mass spectroscopy for 90 days. In vivo release of TA was measured in aqueous humor, vitreous, and retina-choroid at 1, 2, 4, 8, and 12 weeks after intrascleral implantation in 20 rabbit eyes. Implant toxicity and biocompatibility were evaluated by slit lamp examinations, indirect ophthalmoscopy, intraocular pressure measurements, electroretinography, and histological examinations. In vitro studies demonstrated that the implants released TA in a controlled manner over 90 days. In vivo, TA was detected in aqueous humor until 4 weeks and in retina-choroid until 8 weeks after implantation, but was detected constantly over 12 weeks in vitreous. No significant retinal toxicity was observed. These results suggest that the devised intrascleral implant offers a promising controlled release system for the delivery of TA to the posterior segment of the eye.