The ¹³C-NMR spectra of 1-N-[(S)-4-amino-2-hydroxybutyl]kanamycin A (butikacin) (Fig. 1, 1b) and some of its related compounds have been recorded and are tabulated, assigned and discussed. The chemical shifts of many of the carbon nuclei are shown to be reasonably invariant amongst this series of compounds. A procedure is described for the determination of the (R, S)-epimer ratio of kanamycin A derivatives which have N-substituted groups containing a chiral centre.