Each year, 600–700 children are diagnosed with cancer in the Netherlands. Over the last decades, the overall long-term survival of childhood cancer has increased up to ~75%. Due to the expansion of the childhood cancer survivor population, chronic health sequelae resulting from cancer and its treatment have become more prevalent and require our attention. Approximately 75% of the childhood cancer survivors have developed at least one long-term complication of cancer treatment. Gonadal dysfunction is one of the important late effects. The impact of cancer treatment on gonadal function has extensively been studied. However, the extent of loss of gonadal function differs between equally treated childhood cancer survivors. Information on determinants of ovarian function in childhood cancer survivors other than previous cancer treatment is largely lacking. Therefore, in this thesis we aimed to identify determinants of gonadal function and its potential recovery after childhood cancer, and, where possible, to evaluate alternative fertility options for survivors of childhood cancer.