Mycobacterium avium complex (MAC) is thought to be the most common disseminated bacterial opportunistic infection in AIDS, with clinical prevalence estimates ranging from 15 to 50 percent of all AIDS patients. Clarithromycin, a new macrolide antimicrobial agent, has demonstrated activity against MAC both in the laboratory and in animals. Clinical experience treating AIDS patients with clarithromycin for disseminated MAC is limited. However, early studies have indicated few adverse effects and some improvement in clinical symptoms scores and Karnofsky performance scores over placebo treated patients.