We report the case of a 55-year-old man with non-small-cell lung cancer who underwent radiation, chemotherapy with carbotaxol and paclitaxel, and left upper lobe removal 2 years prior to evaluation. He was referred for disabling orthostatic hypotension (113/69 mm Hg supine and 66/47 mm Hg standing after 10 minutes) without a compensatory heart rate increase (57 to 59 beats per minute), fatigue, and constipation with episodes of ileus. Clinical examination showed mild ptosis bilaterally, fatiguable neck flexor weakness, and hip flexor weakness. Blood pressure response to Valsalva maneuver was abnormal with an absence of phase 4 overshoot and a Valsalva heart rate ratio of 1.04. Plasma norepinephrine level was low (79 pg/ml supine, 330 pg/ml standing). Single-fiber electromyography of the right extensor digitorum communis revealed normal mean consecutive difference (jitter) but several pairs exceeded a jitter of 100 mus. Antibodies against muscle acetylcholine receptor [(AChR) 0.66 nmol/L, normal <0.02 nmol/L] and ganglionic AChR (0.34 nmol/L, normal <0.02 nmol/L) were present. Treatment with plasma exchange normalized responses to standing posture (105/68 supine to 118/82 mm Hg standing, 66 to 79 beats per minute), to Valsalva (normal blood pressure overshoot, hazard ratio 1.47), norepinephrine (194 pg/ml supine, 763 pg/ml standing), and jitter measurements. We conclude that autoimmune autonomic ganglionopathy and myasthenia gravis can coexist and suggest that the latter should be excluded in patients with autoimmune autonomic ganglionopathy who complain of fatigue that shows improvement with non-supine rest.