This comprehensive resource offers an explanation of genetic mental retardation syndromes and how they affect behaviour. Four major syndromes - Down, Williams, Fragile X and Prader-Willi - and several lesser-known syndromes are covered, with in-depth information on genetic causes, physical and medical features, speech and language issues, prevalence, cognitive profiles and adaptive and maladaptive behaviours. Researchers and practitioners - including mental health professionals, educators, speech-language pathologists and caregivers - should get the research-based information they need to improve individuals' educational, personal, occupational and residential situations and to create wider community inclusion.