Every year, 3000 women in the Netherlands are treated with in-vitro fertilisation (IVF), and results from studies suggest that the offspring of these women do not have a heightened risk of cancer. Between November, 2000, and February, 2002, we diagnosed retinoblastoma in five patients born after IVF. To calculate the relative risk of the disease, we assumed that the proportion of children conceived by IVF in the Netherlands is between 1.0 and 1.5%, and that the five patients who we diagnosed with the disease represent all new cases in the Netherlands during that period. Relative risks for retinoblastoma were significantly raised (7.2 [95% CI 2.4-17.0], and 4.9 [1.6-11.3], for 1% and 1.5% rates, respectively). This possible association of an increased risk of retinoblastoma in a population-based study needs to be established.