The authors describe 7 new cases of Angelman syndrome (AS: 3 males and 4 females) diagnosed on the basis of clinical features (dysmorphic facial features, severe mental retardation with absent speech, peculiar jerky movements, ataxic gait and paroxysms of inappropriate laughter) and neurophysiological findings. Failure to detect deletion of the long arm of chromosome 15 or the absence of epileptic seizure were not considered sufficient to exclude a diagnosis of AS. Feeding problems, developmental delay and early signs of ataxia, especially tremor on handling objects and unstable posture when seated, proved effective as clinical markers for early diagnosis of AS. The EEG patterns characteristic of AS were found within the first 2 years of life (under 18 months in the majority of cases). The authors conclude that AS should be included in differential diagnosis in a child aged under 12 months having cryptogenic psychomotor retardation with prevalent language compromise. Repeat EEG recordings are needed to check for the typical trace, and cytogenetic investigations are mandatory.