The purpose of this study was to compare short termin vitroandin vivobiodegradation studies with low purity Mg (> 99.94 %), Mg-10Gd and Mg-2Ag designed for biodegradable implant applications. Threein vitrotesting conditions were applied, using (i) phosphate buffered saline (PBS), (ii) Hank’s balanced salt solution (HBSS) and (iii) Dulbecco’s modified eagle medium (DMEM) in 5 % CO2 under sterile conditions. Gas evolution and mass loss (ML) were assessed, as well as the degradation layer, by elemental mapping and scanning electron microscopy (SEM).In vivo, implantations were performed on male Sprague-Dawley rats evaluating both, gas cavity volume and implant volume reduction by micro-computed tomography (µCT), 7 d after implantation. Samples were produced by casting, solution heat treatment and extrusion in disc and pin shape for thein vitroandin vivoexperiments, respectively. Results showed that when the processing of the Mg sample varied, differences were found not only in the alloy impurity content and the grain size, but also in the corrosion behaviour. An increase of Fe and Ni or a large grain size seemed to play a major role in the degradation process, while the influence of alloying elements, such as Gd and Ag, played a secondary role. Results also indicated that cell culture conditions induced degradation rates and degradation layer elemental composition comparable toin vivoconditions. Thesein vitroandin vivodegradation layers consisted of Mg hydroxide, Mg-Ca carbonate and Ca phosphate.