Two patients are described in whom myasthenia gravis was associated with systemic lupus erythematosus. The review of the literature shows that such association is not frequent and that it affects mostly women (6 women:1 man), and that myasthenia gravis usually precedes lupus erythematosus. Thymectomy was a precipitating factor in 25% of the cases. Most of those patients present with general symptoms rather than with dermatologic signs.