Nasal washings from patients receiving phenytoin and from healthy controls were investigated. The concentrations of immunoglobulins and albumin were determined by single radial immunodiffusion. Epileptic patients treated with phenytoin had a higher IgA concentration in nasal washings than controls, 174 × 10−3g/1versus114 × 10−3g/1. The IgG concentration was also significantly higher in the phenytoin‐treated patients compared to the controls. IgM was detected in nasal washings from 41% of phenytoin‐treated patients and from only 11% of the controls.To exclude the effect of exudation of plasma proteins caused by inflammation, the ratio IgA to albumin was calculated and the median of this ratio estimated both for patients and controls. For patients taking phenytoin as their only drug, the median was 1.89versus1.23 in the controls.There was no relation between the serum concentration of IgA and the ratio between IgA and albumin concentrations in nasal secretions. However, patients with serum IgA deficiency had low concentrations of IgA in the nasal secretion and a reduced IgA to albu