A child with Sturge-Weber syndrome and a left occipital leptomeningeal angioma developed focal seizures at 6 years of age that responded initially to oxcarbazepine. After 7 months of seizure freedom, the patient developed typical myoclonic-astatic seizures associated with generalized electrographic discharges, which worsened as oxcarbazepine was increased. The seizures and electroencephalogram improved dramatically in 3 weeks as the oxcarbazepine was withdrawn and valproic acid was initiated. This case demonstrates the importance of recognizing that children with epilepsy due to focal lesions can develop secondary bilateral synchrony that can be aggravated by medications that are effective for partial seizures. In such cases, treatment with a broad-spectrum antiepileptic may be advantageous.