A 13-year-old girl had a reversible frontal syndrome secondary to partial complex seizures. She developed sudden and dramatic behavioral changes including sexual disinhibition, loss of concern for personal hygiene, physical and verbal aggression, and pressured and tangential speech. Although the basic neurologic examination was normal, neuropsychological testing revealed selective impairment on tasks sensitive to frontal dysfunction with relatively normal performance on other tests. This case demonstrates that a frontal syndrome can be caused by partial complex seizures and that behavior comparable to that observed in adults with frontal dysfunction may occur in young adolescents.