This paper reviews Angelman syndrome (AS) with regard to the clinical features in childhood and adulthood, epileptic seizures and EEG findings, neuroimaging studies and the present knowledge on the genetic mechanisms underlying this syndrome. Different clinical phenotypes and genotypes of AS are described, including chromosome 15q11-13 deletion, uniparental disomy, methylation imprinting abnormalities and mutations in the UBE3A gene.