Even though phototherapy is an effective means of treating hyperbilirubinemia, adequate binocular shields are essential to prevent light hazard of retina during phototherapy. The phototherapy to young albino rabbits was performed under various conditions; exposured for 12, 24, and 48 hours, continuity or intermittence of irradiation, and use of shields. Although there was no definite pathologic change in indirect ophthalmoscopic examination, severe damage was seen at electron microscopic level. In all experimental groups, swelling and edema of photoreceptor were seen. at right after phototherapy. Futhermore, more severe damage was seen in case of intermittent irradiated group and prolong exposed group. In mydriatic eyes, severity of damage was similiar to non mydi iatic eyes, but area of retinal damage was more extensive than non-mydriatic eves.. In control group which was protected by binocular shields during phototherapy, no significant abnormality was found.