Treatment is randomly assigned so that twice as many patients receive clarithromycin at the lower dose as at an intermediate dose for 12 weeks. Once data becomes available to support dosing patients with clarithromycin at the highest dose, then treatment will be randomly assigned so that twice as many patients receive clarithromycin at the highest dose as at the intermediate dose. Sixteen patients per group (48 patients in all) will be enrolled. Patients exhibiting clinical improvement or clinical cure while on this trial will be allowed to continue on therapy for an additional 6 months. Patients will have clinical evaluations (including the Karnofsky Performance Scale), laboratory evaluations (hematology and chemistry), and blood cultures for MAC performed monthly.