Three cases of unilateral retinoblastoma with late bilateralization are presented in this study. The rare occurrence of this event underlines the need for prolonged follow-up in the fellow-eye, even in the absence of familial retinoblastoma. In these three cases, the first affected eye was enucleated after a diagnosis made at three months, sixteen months and three years of age. New tumors appeared in the second eye when the children were sixteen years old in one case and five years old in two cases.