Intrathecal baclofen therapy is increasingly used to alleviate medically intractable spasticity in children with cerebral palsy, spinal cord injuries, and generalized dystonia. Complications like overdose or withdrawal can occur and could be the result of pump malfunction (device-related) or refilling and programming mistakes (human errors). This report describes a case, with emphasis on electroencephalographic changes, of a 12-year old male on long-term intrathecal baclofen therapy who had sequential occurrence of both acute inadvertent baclofen overdose followed by withdrawal symptoms. During baclofen intoxication, electroencephalography documented periodic generalized epileptiform discharges, occasionally followed by intermittent electro-decremental responses on a background of diffuse delta slowing (1-2 Hz). During withdrawal, mild generalized slowing during wakefulness was observed along with the appearance of high-amplitude, sharply contoured delta activity resembling frontal intermittent rhythmic delta activity in sleep. To our knowledge, this temporal profile of electroencephalographic features during baclofen intoxication followed by withdrawal has not been described before in pediatric patients. It is important for treating physicians to recognize the evolution of this electroencephalographic pattern in order to avoid misinterpretation of diagnosis and prognosis.