Cyclic isomaltooligosaccharides (CIs) usually consist of 7 to 12 glucose units, although only CI-10 has strong inclusion complex-forming ability. Four Bacillus strains and two Paenibacillus strains were isolated as novel CI-producing bacteria. Among these, five strains produced small amounts of CI-7 to CI-9, but mainly produced CI-10 to CI-12. Larger CIs, up to CI-17, were also identified.