The current authors present the case of a 68-yr-old female patient who developed severe respiratory failure after medication with ciprofloxacin for acute urinary tract infection. A chronic subdural haematoma was surgical evacuated. Postoperatively, an acute urinary tract infection was treated with ciprofloxacin. Six days later, C-reactive protein was rising and the patient was suffering from intermittent high fever, dyspnoea and severe hypoxaemia. The high-resolution-computed tomography (HRCT) showed an interstitial lung disease in the anterior upper lobe on the left side as well as in the lingula. Assuming a bacterial infection amoxyl/clavulanic acid was started which did not improve the clinical symptoms. Bronchoalveolar lavage revealed a marked lymphocytosis (87%). Analysis for typical bacterial infections, Tuberculosis, Mycoplasma, Chlamydia and Legionella spp. were all negative. Another HRCT scan was made because of worsening of symptoms and this showed rapidly progressive infiltrates in most lobes. An open lingular biopsy showed an interstitial lymphoplasmocytotic infiltrate with some eosinophilic granulocytes and a few scattered giant cell granulomas, consistent with hypersensitivity pneumonitis. The patient's symptoms rapidly improved with systemic corticosteroid therapy and another HRCT scan revealed complete remission of pulmonary infiltrates. Ciprofloxacin can induce interstitial pneumonitis with acute respiratory failure. This is an important fact considering that ciprofloxacin is a widely used antibiotic agent in treatment of urinary tract infection.