Patients with symptomatic epilepsy due to hypothalamic hamartomas often are compromised not only by pharmacoresistant epileptic seizures but also by behavioral disturbances and cognitive dysfunction. We report the effect of successful treatment with stereotactic interstitial radiosurgery by intrahypothalamic implantation of 125I seeds on behavior and subjective handicap. In all patients rendered seizure-free or suffering only from auras, improvement of behavior was reported by parents and colleagues or schoolteachers. Parents' ratings according to the Child Behavior Checklist showed improvements with respect to social problems and attention. Self-ratings of quality of life by adult patients showed improvements in activities, working situation, and self-perception. These improvements were not observed in patients in whom clinically manifest seizures and interictal EEG discharges persisted after radiosurgery.