A study of 30 strains ofAcetobacter species from diverse sources such as air, soil, various fruits, fermented liquors and animal excreta was attempted. By a detailed characterization of the isolates, they could be divided into 5 groups and identified as species ofA. aceti, A. xylinum, A. pasteurianum, A. melanogenum, A. industrium, A. oxydans, A. aceti viscosum, A. aceti roseum, A. rancens and their variants. Detailed descriptions of the less known species are presented to supplement the information available in appendix to the genus given in theBergey’s Manual. The description of a group of 6 strains which possess the unusual property of fermenting several carbohydrates with the production of acid and gas—a property not thus far ascribed toAcetobacter species—is also given.