Diphenylhydantoin (DFH) treatment for epileptic patients has shown adverse effects such as malignant lymphadenopathy, systemic lupus erithematosus, periarteritis nodosa and recently immunological alterations such as a decreased lymphocytic response to fitohemaglutinin and serum IgA concentration, therefore we thought DFH effect on secretory IgA would be an important finding. This phenomenon might imply a defect in resistance local mechanisms for infection. Two groups of patients were studied: a) 25 children with an established diagnosis of epilepsy, "grand mal" type, that received anticonvulsive treatment with DFH for six months and b) 25 children with a diagnosis of infectious meningoencephalitis that required DFH to control convulsive crisis. Patients with a history of recurrent infections, lymphadenopathies, hepatosplenomegaly, drug allergy, collagenopathies and immunodeficiency were ruled out from this study. In all patients T and B lymphocytes, serum IgA, saliva and duodenal fluid and IgA determinations were made. Results show IgA concentration decrease in saliva and duodenal fluid of epileptic and meningoencephalitic patients (p less than 0.05), as well as lymphocyte T depression in epileptic and non epileptic patients treated with DFH (p less than 0.001).