The immunological status of five children with West syndrome consequent to previous cerebral lesions was investigated. Three children had West syndrome and two were in transition from West to Lennox-Gastaut syndrome. All of them showed cellular immunological deficiencies in the following tests: sensitization to DNCB, intracutaneous reaction to PHA, inhibition of leucocyte migration, blastic transformation of lymphocytes, T and B lymphocytes in peripheric blood and levels of serum immunoglobulins. These immunological deficiencies, of different degrees of severity, were associated to frequent infections in these children. A possible association between the immunological deficiencies and autoimmunity is discussed.