A case of 34 year old man with lung involvement secondary to chronic exposure to welding with tin oxide. The patient consulted for a four-month history of dry cough associated with mild dyspnea and occasional wheezing without improvement with bronchodilator therapy and appearance of ground glass pulmonary opacities towards the upper lobes. In a transbronchial lung biopsy there are anthracosis areas with brown macrophages without fibrosis, findings consistent with stannosis. This is a rare disease that is associated with a benign course and should be recognized within the group of occupational diseases to define the prognosis of the patient. (Acta Med Colomb 2013; 38: 273-276).