A case of pneumonitis following exposure to Mycobacterium avium intracellulare in an indoor home spa (hot tub) is presented. The patient complained of recurrent dyspnoea and wheezing. High-resolution CT showed centrilobular ground-glass nodules. Pathological correlation showed interstitial and bronchiolocentric granulomata. Biopsy cultures grew M. avium intracellulare. The patient condition improved following cessation of hot tub use.