The new concept of retinoma, or retinocytoma, brings up the rare 'spontaneous regressions' long-reported in the literature. Systematic investigation of all relatives of children suffering from retinoblastoma is showing up more and more retinoma cases undetected until now. From 1975 to 1990 the authors have identified 11 retinoma cases amongst 103 retinoblastoma patients and their families. The average age of the retinoma patients is 23 years with a mean follow-up of four years. There are four bilateral cases, one of which with phthisis bulbi, three unilateral retinomas associated with retinoblastoma of the fellow-enucleated eye, and four unilateral cases. Of the 11 retinomas, seven patients have a family history of retinoblastoma. Of the seven patients of procreating age, 16 offspring, three abortions and two miscarriages are noted. Of the 16 offspring, 12 developed retinoblastoma, 11 of which bilaterally. One 21-year-old patient presented in the process of malignant transformation. A child, enucleated for retinoblastoma of one eye and showing lesions conforming to retinoma in the fellow eye at two years of age, suffered an osteosarcoma when nine years old. The authors' data show that retinoblastoma and retinoma follow the same genetic changes and consequently require the same investigation and follow-up. This study indicates a frequency of retinoma of 10% amongst retinoblastoma patients and their families which is higher than that usually quoted.