Recovery rates of selected behaviors following intracarotid sodium amobarbital injection were examined in 17 patients with unilateral focal temporal lobe epilepsy. Left hemisphere injections resulted in more prolonged disruption of naming (p less than 0.00001), reading (p less than 0.0001), matching-to-sample behaviors (p less than 0.05), and short-term recognition memory for pictures (p less than 0.0001) and words (p less than 0.0003) than did right hemisphere injections. In addition, recovery of behaviors was prolonged if the injection was administered to the hemisphere contralateral to that with the primary seizure focus (p less than 0.005). A trend toward a similar pattern was seen in the postinjection electroencephalogram with the maximum slowing found in the injected hemisphere prolonged if the epileptic focus was in the contralateral hemisphere (p = 0.06). These findings suggest a negative effect of an epileptic lesion on the contralateral hemisphere.