A new type of heroin HCl seized in Australia was examined by stable isotope analysis. The final origin/process classification of these samples by chromatographic signature profiles of the impurity/manufacturing by-products was previously determined to be “unknown” by two independent national laboratories. Various drug enforcement authorities speculated that the heroin might be from a new region or new illicit process due to the unusual chromatographic impurity profiles that were present. Samples from 20 different kilogram packages were examined for isotopic content to determine if the samples fit isotopic patterns of known origins or if they were unique to any known origins. Authentic specimens from Southeast Asian (N=59), Southwest Asia (N=37), South America (N=104), and Mexico (N=21) we concomitantly examined for comparison purposes. Both continuous flow elemental analysis-isotope ratio mass spectrometry and gas chromatography-isotope ratio mass spectrometry techniques were utilized. Heroin samples were also converted to morphine, without apparent isotopic fractionation, utilizing methanolic HCl for gas chromatography-isotope ratio mass spectrometry. The Pong Su samples were found to be isotopically and isotopically/alkaloidally distinct from the known origin/process classifications of Southwest Asian, Southeast Asian, South American, and Mexican.