Patients with Angelman syndrome (OMIM # 105830) are generally thought to have normal brain imaging studies except for occasional minor cerebral atrophy. We report 9 patients with genetically proven Angelman syndrome, who were examined by magnetic resonance imaging (MRI) between the ages of 7.5 months and 5 years. MRI in the 5 patients examined during infancy revealed myelination delay and a deficit of white matter. Retarded and/or abnormal myelination in Angelman syndrome seems to be a common finding that may be diagnostically misleading. This is particularly important in the evaluation of infants with possible Angelman syndrome, who present with nonspecific clinical features and have not yet developed the characteristic behavioural, language, and movement abnormalities.