Stimulants are an effective treatment frequently prescribed for attention-deficit-hyperactivity disorder (ADHD), but they commonly are believed to lower the threshold for seizures. Although several studies have revealed that stimulants do not exacerbate well-controlled epilepsy, there is a paucity of data about seizure risk in nonepileptic children treated with stimulants. Two hundred thirty-four children (179 males, 9.1 +/- 3.6 years of age; 55 females, 9.6 +/- 3.9 years of age) with uncomplicated ADHD received electroencephalograms (EEGs) performed in our institution. Thirty-six patients (15.4%) demonstrated epileptiform abnormalities, and 198 (84.6%) demonstrated normal or nonepileptiform EEGs. Rolandic spikes accounted for 40% of the abnormal EEGs and 60% of those with focal abnormalities. Stimulant therapy was elected by 205 of 234 patients (87.6%). Seizures occurred only in the treated group, in one of 175 patients with a normal EEG (incidence 0.6%, 95% confidence intervals 0%-1.7%) and three of 30 treated patients with epileptiform EEGs (incidence 10%, 95% confidence interval 0%-20.7%). Seizures occurred in two of 12 children (16.7%) with rolandic spikes. These data suggest that a normal EEG can be used to assign children with ADHD to a category of minimal risk for seizure. In contrast, an epileptiform EEG in neurologically normal children with ADHD predicts considerable risk for the eventual occurrence of seizure. The risk, however, is not necessarily attributable to stimulant use.