Three patients with chronic obstructive lung disease (COPD) and myasthenia gravis whose pulmonary symptoms were worsened by therapy with cholinesterase inhibitors were improved by inhaled ipratropium bromide. Two had increases in FEV1 (19 percent, 35 percent) and specific conductance (106 percent, 81 percent) and reductions in dyspnea. The third had no change in airflow with ipratropium, but improved due to decreased bronchial secretions which had limited the use of cholinesterase inhibitors. In contrast, beta agonist bronchodilators had no effect in any of these patients. This experience suggests that ipratropium may be the bronchodilator drug of choice in patients with obstructive lung disease aggravated by cholinesterase inhibitors.