Gas desorption spectrometry has been used to study the behavior of implanted noble gas ions in silicon. Results of low dose Ar implants followed by thermal desorption has shown the release of argon in Si from distinct surface related trapping sites, from substitutional argon (ArV) and from larger Ar-V clusters. This information gives an insight into the response of the silicon lattice to the Ar implants. For higher Ar doses, the effects of amorphization are clear in the desorption spectra and lead tò a method of measuring the recrystallization velocity during epitaxial regrowth (v=2×106 exp(−2.8 eV/kT). A similar value was found for thin sputtered Si films. The paper discusses high dose Ar saturation phenomena and describes the use of helium implants to probe defects and defect structures, such as bubbles and voids, in silicon.