Pulmonary fibrosis is a frequent and serious complication of scleroderma whose pathophysiology remains poorly understood. The alveolar structures are infiltrated by activated chronic inflammatory cells, alveolar macrophages and polymorphonuclear neutrophils in particular and these could play a determining role. We have studied the state of activation of alveolar macrophages and monocytes circulating in these patients who presented with scleroderma and interstitial pulmonary involvement and also in healthy subjects. The neutrophil alveolitis observed in the patients is accompanied by a raised level of interleukin-8 secretion by the alveolar macrophages compared to the healthy subjects. Interleukin-8 is an important chemotactic molecule for polymorphonuclear neutrophils in the lung. The neutrophil alveolitis is accompanied by a breakdown in the equilibrium of elastase-antielastase which could participate in the development of alveolar lesions leading to fibrosis. In addition to the activation of macrophages, there is an activation of monocytes marked by the increase in secretion of interleukin-6 and interleukin-8 in vitro during the progression of the disease of scleroderma. Thus, alveolar inflammation is integrated with the overall systemic inflammation whose causes remain unknown.