The case of a 6 year old girl with Lennox-Gastaut's syndrome caused by cysticercosis of the central nervous system (CNS) is reported. The illness began at 18 months of age with right sided convulsions during an upper respiratory tract infection. Electroencephalogram (EEG) showed depression of rapid rythm on the left side. There was progressive mental deterioration, right spastic hemiparesis and aphasia. Then the EEG showed progressively worsening of generalized irritative activity, with spikes and sharp waves. At the age of 3 years there appeared flexion myoclonic spasms and EEG showed a hypsarythmic pattern. Both clinical and EEG picture allowed the diagnosis of West's syndrome. In the following months the patient presented akinetic seizures, myoclonic jerks and generalized convulsive seizures with turning of the head to the right. EEG revealed slow spike-waves thus leading, at this time, to the diagnosis of Lennox-Gastaut's síndrome. Brain cysticercosis was diagnosed on the basis of 8 repeated positive cerebrospinal fluid examinations.