The total structures of capreomycins IA and IB were determined mainly from the results of the comparative study on the NMR spectra of capreomycins and tuberactinomycins, resulting in a revision of the formerly proposed structure. The beta-lysine residue as a branched part was revealed to be linked with the beta-amino group of the alpha, beta-diaminopropionic acid residue in the cyclic pentapeptide moiety in a different manner than in tuberactinomycins.