The association of systemic lupus erythematosus (SLE) and myasthenia gravis is well known. However, the association between SLE and Lambert-Eaton myasthenic syndrome (LEMS) is described in only 2 cases. We describe the case of a 31-year-old woman with SLE who presented with severe, predominantly proximal muscle weakness of subacute onset. The diagnosis of LEMS was based on her distinctive clinical and electrophysiological findings. She was treated successfully with plasmapheresis and oral prednisone. She remains in remission 6 months after this episode.