Few data are available on the risk of seizures in young children with developmental problems. A retrospective evaluation of 1,946 children 0-5 years of age referred to the Tel Aviv Child Development Center (CDC) between 1981 and 1990 was performed. The study was undertaken to determine the cumulative risk of unprovoked seizures in children referred to a CDC and to assess the risk factors associated with seizures in these children. The center serves the Tel Aviv area for a variety of developmental disabilities. Cumulative risk of seizures and risk factors were assessed using Kaplan-Meier methodology. Unprovoked seizures occurred in 58 patients (3%), including 10 with a single seizure and 48 with two or more seizures. Risk factors for seizures included cerebral palsy (CP) (relative risk [RR] = 28.7), neonatal seizures (RR = 15.2), mental retardation (MR) (RR = 7.8), febrile seizures (RR = 7.7), autism (RR = 3.2), and prematurity (RR = 2.7). The cumulative risk of seizures by age 5 years in children with MR, CP, and MR plus CP was 8%, 47%, and 68%, respectively, compared with 1% in those without MR or CP. On multivariate analysis, CP, MR, prior febrile seizures, and prematurity were associated with an increased risk of seizures. The risk of experiencing unprovoked seizures by age 5 in children with developmental disabilities is 3%, which is fourfold greater than that of the general population. Much of this increased risk is limited to selected subgroups with major disabilities. However, if neither MR nor CP is present, the 1% risk of developing unprovoked seizures by age 5 in children with other developmental problems is not substantially different from that expected in the general population.