The retinoblastoma is the most frequent intraocular tumour in early childhood occurring in a hereditary as well as non-hereditary form and showing an increasing incidence since the beginning of this century, which has nowadays stabilized near 1/16,000. Further differentiation is necessary in view of unilateral and bilateral as well as sporadic and familiar occurrence. Estimates of the relative frequencies of the resulting different groups are given und summarized in two tables in two different aspects.