The purpose is to determine the effectiveness of photodynamic therapy of experimental choroidal melanoma in rabbits using hematoporphyrin monomethyl ether (HMME).Pigmented choroidal melanomas were established in 46 New Zealand albino rabbit eyes. The animals were treated with daily injection of cyclosporine A. The tumors were followed up with funduscopic examination and ultrasonography until they were 1.5 to 4.6 mm in height. Then the rabbits were divided randomly into two groups. In the treatment group, 41 rabbits were injected intravenously with hematoporphyrin monomethyl ether (HMME, 10 mg/kg). 3 hours later, the tumors were irradiated at 630 nm through an He-Ne laser at estimated total light doses of 60 approximately 150 J/cm(2). Control animals (5 rabbit eyes) were treated with light only (2 rabbit eyes), photosensitizer only (2 rabbit eyes), or observation only (1 rabbit eyes). Each animal then was followed up for 4 to 5 weeks with indirect ophthalmoscopy, ultrasonography, and fundus photography (16 rabbit eyes among the treatment group were extirpated for pathologic examination 24 hours or 1 week after the treatment). In the end, all the rabbits were sacrificed and the pathologic examinations were performed.With the fluences of >or= 70 J/cm(2), all the tumors regressed evidently. With the fluence of 60 J/cm(2), not all the animals showed complete tumor arrest. In the control group, all the tumors showed continuous growth and filled most of the vitreous cavity in 2 to 3 weeks.The photodynamic therapy with homemade photosensitizer HMME may have a role in the treatment of pigmented choroidal melanomas.