One of the following three chemotherapeutic regimens (Table 1) was commenced within 3 months after the patient's initial presentation at the hospital, depending on the term: regimen A, consisting of CAM, 400 mg/d (9.5 mg/kg), EB, 750 mg/d (17.8 mg/kg), and RFP, 450 mg/d (10.7 mg/kg), applied from January to August 1999 (term A); regimen B, based on the results of regimen A, consisting of CAM, 800 mg/d (17.6 mg/kg), EB, 750 mg/d (16.7 mg/kg), and RFP, 450 mg/d (10.0 mg/kg), applied from January to December 2000 (term B); and regimen C, based on the results of regimen B, consisting of CAM, 800 mg/d (17.9 mg/kg), EB, 1,000 mg/d (22.7 mg/kg), and RFP, 600 mg/d (13.4 mg), for the first 2 months followed by EB, 750 mg/d (16.7 mg/kg), applied from January 2002 to April 2004 (term C). Chemotherapeutic periods were 18 months for each regimen. During terms A, B, and C, 24, 33, and 45 patients, respectively, with MAC pulmonary disease presented at our institute. Among them, 18, 21, and 27 patients were treatment naive, and 10, 13, and 15 of those patients, respectively, met the following inclusion criteria: HIV-seronegative; never-smoker without any preceding or underlying diseases, such as COPD, lung cancer, healed tuberculosis, or other lung disease, based on pulmonary function testing and chest CT scan findings; coexistence of chronic sinusitis ruled out by an otolaryngologist; no optic neuritis confirmed by an ophthalmologist; ability to visit the outpatient clinic regularly; and ability to participate in sputum collection, including voluntary expectoration of sputum, induction of sputum by inhaling a 3% sodium chloride solution, or production of sputum samples as needed or on demand. Prior to the initiation of treatment, all patients were informed of the diagnosis, the typical clinical course of the disease, and the potential side effects of the chemotherapy, including optic neuritis due to EB and GI disorders, such as appetite loss, nausea, diarrhea, and liver dysfunction. After initiation of chemotherapy, patients who had major toxicity necessitating early cessation of therapy were excluded.