In 40 patients with metastatic brain tumor and acute lymphoblastic leukemia reveived whole brain irradiation, the dose delivered to the eyelens was measured using T.L.D. chips applied on the eyes as usual shield. The dose tothe eyelens was expressed the relative dose to the mid brain dose. Radiotherapy was administered using Co-60 teletherapy with bliateral whole brain irraditaion. The resuls are as follows; 1. The dose to the right eye fromits incipient field is 16.6% of tumor dose while the dose to the same eye from the opposite filed is 41.2%. Onleft eye, 19.2% from incipient field whild 39.2% from the oppposite field. 2. Total received dose to right andleft eyes is 28.9%, 29.8% of tumor dose respectively. 3. Comparing lens shield group with orbit shield group received dose is 22.5%, 15.8% of tumor dose, respectively. 4. The dose delivered to the eyelens in ipsilateralside depends upon internal scattering, location of lead shield and penetrating dose of lead in itself. The dose incontralateral side depends upon divergency of radiation beam and patient's malposition. 5. The dose to the eyelens should be less than 10% of tumor dose with adequate shield, also not missing the chance of leptomeningeal recurrence because of overshielding.