RESUMEN
BACKGROUND: Unprecedented changes in both the scale and the complexity of international migration have led to international concern and controversy over the assessment of age in children and young people subject to immigration control or seeking asylum who say they are children yet have no documents to prove their stated age. SOURCES OF DATA: The article reviews the existing evidence on the reliability of medical and non-medical techniques for the assessment of chronological age. AREAS OF AGREEMENT: There is evidence that radiography (X-rays) of bones and teeth, which is increasingly relied upon by immigration authorities, is imprecise, unethical and potentially unlawful, and should not be used for age assessment. AREAS OF CONTROVERSY: Medical techniques including X-rays continue to be relied upon in the absence of an alternative approach resulting in legal challenges and uncertainty for children and young people. AREAS TIMELY FOR DEVELOPING RESEARCH: Further work is needed to establish a process for age assessment based on a 'holistic' multi-disciplinary approach which focuses not on chronological age exclusively but rather on the needs of children and young people subject to immigration control.