Rifabutin is a spiro-piperidyl-rifamycin derived from rifamycin-S. It is structurally related to rifampin and shares many of its properties. Rifabutin has a broad spectrum of antimicrobial activity. It is considerably more active than rifampin in vitro against the Mycobacterium avium complex (MAC), Mycobacterium tuberculosis, and Mycobacterium leprae. It also is active against most atypical mycobacteria, including Mycobacterium kansasii, but Mycobacterium chelonae is relatively resistant. Rifabutin also is active against staphylococci, group A streptococci, Neisseria gonorrhoeae, Neisseria meningitidis, Haemophilus influenzae, Haemophilus ducreyi, Campylobacter jejuni, Helicobacter pylori, Chlamydia trachomatis, and Toxoplasma gondii. It has poor activity against Enterobacteriaceae and Pseudomonas species. This review focuses on the antimicrobial profile of rifabutin in relation to its pharmacological properties. Special emphasis is placed on its in vitro activity against MAC and other mycobacteria, its efficacy in cell culture and animal models, and its potential as a component of multidrug therapy for mycobacterial and other infectious diseases.