The authors made a collective study of 24 cases of retinoblastoma which were diagnosed by the histopathological examination, in the 16 years period between February, 1963 and January 1979. The sex ratio was 1:1, being 12 cases for both male and female. The sex and age incidences were summarized in Table 2. The youngest cases in this series was 9 month old male, and the oldest was 5 years old male. 8 cases involved the left eyes, and 16 cases involved the right eyes. No record of involvement of both eyes was found in this series. The main presenting clinical findings were cat's eye appearance, exophthalmos, intraocular mass, eye pain and visual disturbance and lacrimation (Table 3). Of the 20 cases in which microscopic slides were available for reexamination, 15 cases showed mainly the endoptytic growth and 5 cases showed exophytic growth. 5 cases exhibited a pronounced rosette formation, 5 cases showed a moderate degree of rosette formation and the remaining 10 cases showed either spare or little tendency for rosette formation. Of the 18 cases, in which histopathological examination of optic nerve was possible, 11 cases showed optic nerve invasions.