Continuous spikes and waves during slow sleep syndrome is characterized by the presence of spike-and-wave discharges in at least 85% of non-rapid eye movement sleep. Associated clinical features vary. Here, features of 10 patients with this syndrome are compared to those in the literature. Patients ranged in age from 4 to 11 years. All patients had predominantly nocturnal partial motor or generalized tonic-clonic seizures; four patients also had daily atonic seizures. All 10 patients had different degrees of neuropsychologic disturbances: 9 patients had low intelligence quotient scores (the 10th, diagnosed attention deficit and hyperactivity disorder, had normal intelligence quotient score); 4 patients had autistic-like features. Apart from mental retardation (7 of 10), physical and neurologic findings were normal. Significant pyramidal signs and microcephaly were detected in two patients, and hypotonia, ataxia, and bilateral pyramidal signs were found in one other. Cranial magnetic resonance imaging findings were normal for 6 patients; the other 4 had some abnormal findings. Continuous spikes and waves during slow sleep syndrome is a rare epileptic syndrome in childhood. A variety of clinical and neurocognitive features were found in patients with continuous spikes and waves during slow sleep syndrome. (c) 2008 by Elsevier Inc. All rights reserved.