The AnaeroPack (Mitsubishi Gas Chemical America, Inc., New York, N.Y.) system was compared with the GasPak (Becton Dickinson Microbiology Systems, Cockeysville, Md.) system and a conventional anaerobe chamber to evaluate the ability of the AnaeroPack system to support the growth of clinically significant anaerobes. The AnaeroPack system requires no catalyst or water, produces no hydrogen, and is oxygen absorbing and carbon dioxide generating. It is simple to use and reduces preparation time to a minimum. One hundred forty clinical isolates obtained from various anatomic sites and 10 American Type Culture Collection type strains were evaluated. Isolates were plated on various media, and bacterial growth was examined after 24, 48, 72, and 168 h of incubation. Criteria for evaluation and comparison of systems included rate and quality of growth, colonial morphology, hemolytic reactions, and pigment production. Results indicate that the AnaeroPack system is highly effective in creating an anaerobic atmosphere. The AnaeroPack system never failed to reduce the methylene blue indicator, while the GasPak system failed 15% of the time. The rate or quality of growth achieved by the AnaeroPack system compared with that of established anaerobic culturing techniques was similar and significantly better for several genera including the Bacteroides fragilis group, Fusobacterium, Clostridium, and Peptostreptococcus. The AnaeroPack system appears to be an excellent alternative to established methods for generating an environment for anaerobic incubation.