Hot tub lung is described as an acute pulmonary illness that is characterized by fever, dyspnea and interstitial nodular infiltrates. Although not entirely clear, the etiology may be a hypersensitivity pneumonitis, an infection secondary to Mycobacterium avium intracellulare (MAC), or possibly both. Herein we describe the most well-characterized physiologic, radiographic, and functional recovery from hot tub lung reported in the literature to date. Pulmonary function testing and CT scans of the chest were obtained after each therapeutic intervention, and the patient had the most dramatic improvement with simply avoiding the hot tub. Prednisone therapy offered minimal further improvement while anti-MAC therapy provided no further improvement. These results are suggestive of a hypersensitivity pneumonitis rather than an infectious etiology.