Abstract: ¹H and ¹³C NMR spectra of d,l- and meso-HM-PAO in different solvents were studied at different resonance frequencies. The ¹HNMR spectra of two diastereoisomers are the same in dimethyl sulfoxide and acetone, but different in chloroform. The ¹³C NMR spectra are different in dimethyl sulfoxide and chloroform. The different ¹H and ¹³C NMR spectra can be used to identify and differentiate these two diastereoisomers. It is also shown that the d,l-HM-PAO stereoisomeric purity in a mixture of these two isomeric forms can be determined with sufficient accuracy by using ¹³C peak areas or heights of their C(5) and C(7) in a routine noise decoupling ¹³C spectrum of the mixture.