The utilization of heptoses and related compounds by bacteria and yeasts was investigated. Most cultures metabolized sedoheptulose, which was the only sugar dissimilated under both aerobic and anaerobic conditions. No other heptuloses were utilized by these organisms. Some cultures were able to oxidize various heptoses to the corresponding heptonic acids and certainAcetobacterstrains produced other compounds. Heptitols were attacked by only theAcetobacterspecies. Heptonic acids were utilized slightly by a few organisms.