Azathioprine (Aza) has been used alone or in combination with steroids for two groups of myasthenic patients. Positive responses were noted in 75% of patients on Aza alone and in 70% receiving the combined regimen. The clinical course of the two groups differed in terms of respiratory crisis and need for plasma exchange. With an appropriate Aza administration schedule side-effects were not a limiting factor to its use. Aza treatment induced a reduction in anti-AchR-antibody level that was correlated with clinical improvement and greatly decreased the need for steroids.