Ten years have passed since the Chernobyl disaster. Five years ago, reports began to appear suggesting an increase in the frequency of thyroid cancer in children living or born in the areas with highest exposure to radioactive contamination. During the past year, data have been published, presented, or submitted that demonstrate the magnitude of the increase in incidence. No increase in childhood leukemia or other cancers has been documented. However, anxiety about the future persists. A rapid government response, including the distribution of potassium iodide to the highest-risk groups, pregnant women and young children, could have prevented the majority of the cases of thyroid cancer.