INTRODUCTION: Angelman syndrome (AS) is characterised by mental retardation, ataxic gait, epilepsy, absence of language and a special series of physical traits behavioural phenotype. Its incidence is estimated as one in every 20,000 individuals. On the basis of discoveries made in molecular biology, patients can be classified as belonging to five types: deletion, paternal uniparental disomy (UPD), imprinting defects, mutation of the UBE3A ubiquitin protein ligase gene and unidentified mechanism (15% 20% of patients). Some studies report significant correlations between the phenotype and the genetic cause. PATIENTS AND METHODS: We reviewed, retrospectively, 37 patients suffering from AS with a positive genetic study and who had been controlled for at least two years in the Neurological Service at the Hospital Sant Joan de D u. Data was collected on physical characteristics, behavioural phenotype, type of communication, sleep disorders and the medication they needed, as well as epilepsy, start age, types of seizures, medication, schooling and social integration. RESULTS: 87% of cases were due to de novo deletion, 8% were caused by UPD, and 5% had their origins in imprinting defects. The average age of diagnosis was 6.5 years. The sleep disorders present in 48% of the patients required medication in 67% of cases, and 95% presented epilepsy. The most frequent seizures were myoclonic, tonic clonic and atonic. The electroencephalogram (EEG) was the characteristic found in the AS in 68%. The most effective treatment was afforded by valproate and clonazepam. CONCLUSIONS: As regards the phenotype, no differences were found according to the genetic alteration. The most effective treatment for the sleep disorders was melatonin. Epilepsy was an almost constant finding in our series, as was cognitive affectation. Lastly, it must be pointed out that educational and socio occupational integration is difficult for patients suffering from AS.