A 44-year-old man with a 24-year history of hard metal lung developed multiple subcutaneous nodules. He was initially treated with prednisolone for 4 years. Then at the age of 35 he was administered prednisolone 40 mg/day for relapse of the disease, followed by immunosuppressant tacrolimus and insulin for steroid-induced diabetes. At the age of 43, he was administered long-term oxygen therapy and prednisolone was increased to 50 mg/day. A biopsy of the subcutaneous nodule revealed infiltration of neutrophils and histiocytes and numerous acid-fast bacilli that were identified as Mycobacterium intracellulare by PCR, but neither Langhans giant cells nor epithelioid granulomas were found. A positive culture of M. intracellulare from sputa, blood, and urine confirmed the diagnosis of disseminated nontuberculous mycobacteriosis. His peripheral CD4 lymphocyte count was 12/µl. Shortly after administration of rifampicin, ethambutol, and clarithromycin, corticosteroid withdrawal syndrome and a decrease in tacrolimus concentration were observed. We increased the dose of prednisolone and tacrolimus to 2-fold and 3.5-fold, respectively. These pharmacological events probably resulted from CYP3A4 induction by rifampicin, in spite of the inhibition CYP3A4 by clarithromycin. Furthermore, rifampicin may decrease the blood concentration of clarithromycin. Finally, the disappearance of subcutaneous nodules and the clearance of M. intracellulare from sputa, blood, and urine cultures were obtained within 3 months.