Nephroblastoma or Wilms tumor is a malignant tumor of the kidney, specific to early childhood, and very different from kidney cancer in adults. With nearly a hundred cases per year on average in France, it occurs most frequently between 1 and 5 years. More than half of nephroblastomas are treated with short chemotherapy followed by surgery (removal of the diseased kidney) and a few weeks of chemotherapy. Slightly more extensive forms should be treated without radiotherapy, but with more intense chemotherapy. About 25% of patients still need irradiation and aggressive chemotherapy. The survival rate is rather high, but the sequelae & side effects due to the treatments are numerous.