D-penicillamine has been used in the treatment of rheumatoid arthritis for years. As a rare complication of this treatment the occurrence of myasthenia gravis has been described, the clinical features of this complication being indistinguishable from that of idiopathic myasthenia gravis. Both D-penicillamine induced and idiopathic myasthenia gravis show elevated titers of acetylcholine receptor antibodies and respond to acetylcholinesterase inhibitor treatment. We report on a patient with rheumatoid arthritis who, under treatment with D-penicillamine, developed severe myasthenia gravis which required temporary acetylcholinesterase inhibitor therapy. 8 months after D-penicillamine was discontinued the acetylcholine receptor antibodies had disappeared and the acetylcholinesterase inhibitors could be withdrawn. Clinical findings and possible pathogenetic aspects of D-penicillamine induced myasthenia gravis are discussed.