A 47 year old woman presented to the emergency department due to persistent productive cough, accompanied by breathlessness on exertion, chest pain and weight loss during the last three months. She was an occasional smoker and had been working as a mushroom grower of the Pleurotus species during the past six months, with an otherwise unremarkable medical history. An earlier chest CT scan, performed forty days previously, revealed bilateral patchy ground glass opacities, more profound in the upper lobes. One month before presentation she underwent bronchoscopy in another hospital and the cytological examination of the collected bronchoalveolar lavage (BAL) demonstrated excessive neutrophilia. She received at that time a course of antibiotic therapy with doxycyclin and amoxicillin/clavulanate, without clinical improvement. During hospitalization in our department, the patient underwent again bronchoscopy with BAL, revealing significant lymphocytosis (32%), additionally to the previously observed neutrophilia (43%). Given the compatible occupational history, the radiologic pattern and the BAL subpopulation analysis, a diagnosis of hypersensitivity pneumonitis was made and the patient was discharged with a recommendation to withdraw from her current occupational activity. Six weeks later, the patient presented evident clinical, imaging and functional improvement.