We studied 15 children with complex partial seizures in whom one or more seizure type was exacerbated during treatment with carbamazepine. The most common seizure type that was exacerbated was generalized atypical absence (11 patients). Four patients had more frequent and severe generalized convulsive seizures. Monitoring with video-electroencephalographic telemetry suggested that the electroencephalogram can be used to predict the risk of seizure exacerbation with carbamazepine. A bilaterally synchronous spike-and-wave discharge of 2.5 to 3 cycles per second is predictive of increased atypical absence seizures with carbamazepine, whereas generalized bursts of spikes and slow waves of 1 to 2 cycles per second suggest a risk of increased generalized convulsive seizures. Carbamazepine should be used with caution in children with a mixed seizure disorder, particularly those with a generalized bilaterally synchronous discharge of 2.5 to 3 cycles per second on the electroencephalogram. The drug should be considered a possible precipitating factor in any child with an increased frequency of generalized convulsive or generalized absence seizures concomitant with administration of this anticonvulsant agent.