A surveillance and epidemiological study, conducted by the US National Cancer Institute (NCI), has shown that recent trends indicate an excess of total retinoblastoma among boys compared to girls. The findings represent a notable contrast to previous reports of a female predominance of retinoblastoma and suggest a potential effect of sex on cancer origin. The authors of the study propose that changes in the availability of prenatal screening for retinoblastoma may have contributed to some of the changes in the incidence patterns.