This investigation of cognitive functioning in patients with symptomatic localization-related (partial) epilepsy prior to administration of antiepileptic medication is part of a nationwide prospective, double-blind study of drug efficacy and longitudinal changes in cognition associated with seizure disorders. Recently-diagnosed patients with complex partial or secondarily generalized tonic clonic seizures, equated for age, education and IQ, were compared with normal controls on a battery of neuropsychological tests: verbal and figural memory measures (Rey auditory verbal learning test, Rey Osterrieth complex figure), and a brief behavioral toxicity battery comprising measures of motor function, concentration and mental flexibility (Lafayette grooved pegboard, controlled word association test, Stroop, paced auditory serial addition test [PASAT]). Control subjects perform significantly better than both groups of seizure patients on several measures of motor speed/integration and memory, specifically the pegboard and the RAVLT learning (3-5) and recall trials. Secondarily generalized seizure patients show greatest impairment. They perform significantly worse than patients with complex partial seizures and control subjects on the controlled word association test and the most demanding Stroop color word trial, both measures of concentration and mental flexibility. These findings document deficits in memory as well as concentration and motor function in complex partial and in secondarily generalized seizure patients prior to treatment with antiepileptic medication.