AbstractLittle is known of the effect of chronic hemodialysis on lung function. In six patients with chronic uremia, we performed pulmonary function tests, sampled arterial blood, and measured the ventilatory response to carbon dioxide inhalation before and after routine hemodialysis. Patients were in the seated position throughout the study period. Routine pulmonary function was normal in all but one patient; a restrictive ventilatory defect was seen in a patient with prior pleuropericarditis and this was independent of fluid status. All patients showed improvement after dialysis in maximum flow rate at 25 per cent vital capacity corrected for changes in vital capacity (V max25%VC/VC) supporting reversible obstruction of small airways. Hypoxemia was not precipitated by dialysis and all patients showed a small improvement in alveolar-arterial oxygen gradient. Although resting hyperventilation was documented in these patients, the ventilatory response to carbon dioxide inhalation was not consistently enhanced before or after hemodialysis.