Myasthenia gravis is an affliction caused by a disturbance in the neuromuscular junction. Patients suffer from skeletal muscle weakness and fatigability, and in the course of the day lose the ability to use certain muscle groups. After a period of rest that ability may be restored, after which a new period of inactivity follows. The basis of the disease is the forming of antibodies against the acetylcholin receptors at the muscle side of the synapses. So, this is essentially an autoimmune disorder. For a minority of the patients the surgical removal of the thymus puts an end to the complaints. For most of patients anticholinesterase medication suppresses the symptoms and allows a normal life. Also immunosuppresive therapy is an option. During a crisis the antibodies can be selectively removed by plasmapheresis. Dental care of the patients urges special consideration.