A case of a 14-yr-old female with necrotizing sarcoid granulomatosis (NSG) is presented. She was referred because of chest pain and malaise, and radiography revealed multiple pulmonary nodules. Her history showed seasonal sensitization to aeroallergens and hay fever. Infectious agents or malignancies did not characterize these nodules. However, she was treated with macrolide antibiotics because of suspected infection with Chlamydia pneumoniae. Open lung biopsy showed histological findings of NSG, with epithelioid granulomatous inflammation, including giant cells, and vasculitis. No further treatment was performed, and symptoms disappeared within a few weeks. The chest radiograph showed gradual improvement. The aetiology of NSG is poorly understood, and is postulated to represent either sarcoidosis or rare forms of pulmonary vasculitis such as Wegener's granulomatosis or the Churg-Strauss syndrome. In the case presented, a coincidence of infection with Chlamydia pneumoniae suggests an involvement of infectious agents in the pattern of formation of immune complexes in the aetiology of NSG.