Four patients were operated for unilateral left eventration of the diaphragm There were two male and two female patients with a mean age of 63.0+/-14.1 years. All of the patients had dyspnea for an average of 6.2+/-2.6 years. Chest X-ray, fluoroscopy, thorax computed tomography (CT) and in one patient magnetic resonance imaging (MRI) were used for diagnosis. Preoperative forced vital capacity (FVC) and arterial blood partial O-2 pressure (PaO2) values were 1.8+/-0.4 L and 73+/-1.4 mm Hg, respectively. Left thoracotomy via 7(th) intercostal space was applied and complete thinned diaphragmatic leaf was found in all patients. In three patients diaphragm was repaired by plication. In one patient after incision of the leaf, imbrication of one layer over the other was done. No morbidity and mortality were seen. Relief of dyspnea was achieved in all patients. Postoperative FVC and PaO2 values were increased to 2.3+/-0.4 L and 86.6+/-2.7 mm Hg, respectively. Surgery for eventration of the diaphragm in symptomatic patients increases FVC and PaO2 values, thus relieves dyspnea.