Abstract Creatine (N-methyl-N-amidinoglycine), creatinine (1-methyl-2-aminoimidazolin-4- one) and a series of 38 of their close structural analogs have been examined using natural abundance 13 C NMR spectroscopy at 25.16 MHz. Both proton-coupled and proton noise- decoupled spectra were recorded. Unequivocal assignments of the carbon resonances could be made in the vast majority of cases. Both 13 C NMR chemical shifts and 1 J (CH) ...