A four-year-old boy with ring chromosome 17 presenting with early-onset, pharmacoresistant epilepsy underwent repeated 24-hour video-EEG monitoring and cytogenetic analyses, including fluorescent in situ hybridization with telomeric and locus-specific probes of chromosome 17. Epilepsy was characterized by nocturnal motor seizures and by prolonged diurnal electrical status epilepticus. The 46, XY, r (17) karyotype was observed in the majority of cell lines. Fluorescent in situ hybridization revealed a deletion at the 17p telomere on the ring chromosome, whereas the 17q telomere and the Miller-Dieker lissencephaly locus were undeleted. The epileptic syndrome observed in this case of ring chromosome 17 resembles the one described in the ring chromosome 20 syndrome, raising the question of the specificity and the pathogenesis of ring chromosome epileptic syndromes. [Published with videosequences].