Thirty-nine children were treated with either phenobarbital (PB) or carbamazepine (CBZ) for newly diagnosed partial onset seizures. Drug selection was randomized in 33 subjects. Parents and the psychologist evaluating the child were blind to drug identity. Psychometric and behavioral evaluations were done at intake and at 6- and 12-month follow-ups. There were no significant differences between drugs in effect on behavior or cognitive function. CBZ caused more systemic problems. There was a trend toward better seizure control with CBZ, but this was not statistically significant. Although individual children in each group had changes in behavior or cognitive status, neither group changed significantly, in either acute or chronic follow-up.