We report a case of a 25-year-old, white, male plaster worker who started developing fever, severe dyspnea and cough during the manipulation of esparto fibers. The functional lung study showed restrictive lung disease and decreased single-breath carbon monoxide transfer lung capacity. High-resolution computed tomography revealed a diffuse 'ground-glass' pattern. The histopathological findings were interstitial inflammation with a marked predominance of lymphocytes and microgranulomas. Bronchoalveolar lavage showed a significant predominance of lymphocytes, with an increase in the level of CD8. Serum precipitins against fungal antigens confirmed that Aspergillus fumigatus was the cause of the patient's hypersensitivity pneumonitis.