Abstract-A series of experiments carried out by Koscheev et al. (1998Koscheev et al. ( , 2001Koscheev et al. ( , 2004Koscheev et al. ( , 2005 showed that the bimodal release of heavy noble gases from meteoritic nanodiamonds can be reproduced by a single implanted component. This paper investigates the implications of this result for interpreting the noble gas compositions of meteoritic nanodiamonds and for their origin and history. If the bimodal release exhibited by meteorite diamonds reflects release of the P3 noble gas component, then the composition inferred for the pure Xe-HL end member changes slightly, the excesses of heavy krypton isotopes that define Kr-H become less extreme, evidence appears for a Kr-L component, and the nucleosynthetic contribution to argon becomes much smaller. After correction for cosmogenic neon inherited from the host meteorites, the neon in presolar diamonds shows evidence for pre-irradiation, perhaps in interstellar space, and a nucleosynthetic component perhaps consistent with a supernova source. After a similar correction, helium also shows evidence for presolar irradiation and/or a nucleosynthetic component. For the case of presolar irradiation, due to the small size of the diamonds, a large entity must have been irradiated and recoiling product nuclei collected by the nanodiamonds. The high 3 He/ 21 Ne ratio (~43) calls for a target with a (C + O)/heavier-element ratio higher than in chondritic abundances. Bulk gas + dust (cosmic abundances) meet this criteria, as would solids enriched in carbonaceous material. The long recoil range of cosmogenic 3 He argues against a specific phase. The excess 3 He in presolar diamonds may represent trapped cosmic rays rather than cosmogenic 3 He produced in the vicinity of the diamond crystals.