A girl of borderline intelligence developed repeated syncopal attacks that were compulsively self-induced, apparently by forced expiration against a closed glottis (Valsalva's maneuver). In addition, she had typical absence seizures triggered by her apneic attacks, which could also be induced by hyperventilation. The absence seizures were suppressed by treatment with valproate sodium, which had no effect on the self-induced apneas. These were considerably improved with fenfluramine hydrochloride treatment, which was also associated with marked improvement of her previously abnormal behavior.