A 57-year-old physician with increasing dyspnoea and hypoxaemia had a high-resolution CT scan of the chest, which disclosed diffuse pulmonary ground glass opacities, more pronounced in the upper lobes with minimal mediastinal lymphadenopathy. Transbronchial biopsy of the right middle and lower lobes was performed, demonstrating varying degrees of well circumscribed organising granulomatous pneumonitis thought to be most consistent with hypersensitivity to nontuberculous mycobacteria. Cultures of water obtained from the patient's home shower were positive for Mycobacterium avium complex. The patient began substituting baths for showers, experiencing some gradual improvement of his symptoms. Subsequently, he installed point-of-use 0.2 micron membrane filters on his shower, and resumed regular showering after installation with continued symptomatic improvement. CT scans at 3 and 18 months revealed improvement and resolution, respectively. Four years later, he continues to shower in filtered home shower water and remains clinically well.