Ribosomal protein S6 (rpS6) is a small protein of 33 kDa, residing in the 40S ribosomal subunit and has drawn much attention since its discovery over thirty years ago. The rpS6 is located downstream of the mammalian target of rapamycin (mTOR) along with the eukaryotic initiation factor 4E (eIF4E)-binding protein (4E-BP1) and is activated through phosphorylation by ribosomal S6Kinase (S6K). The increased phosphorylation of rpS6 leads to enhanced translation of specific mRNAs. The phosphorylation sites have been mapped to five evolutionarily conserved residues. rpS6 has been implicated in different processes e.g. regulation of transcription of 5ｴTOP mRNAs but has also been reported to enhance ribosome biogenesis by connecting the two ribosome subunits and thereby affecting global protein synthesis. Moreover, knockout of S6K results in mice with reduced body size.The aim of this study was to examine the expression of total rpS6 protein as well as phosphorylated rpS6 (PrpS6) residues in denervated hind-limb and hemidiaphragm muscles in mice, using Western blot. An experimental model consisting of 6 days denervated hemidiaphragm muscle (hypertrophic) and 6 days denervated hind-limb muscles (atrophic) was used. The expression of total rpS6 protein was not significantly altered in atrophic muscle (hind-limb), but there was a significant increase in the expression of phosphorylated rpS6 protein in atrophic muscle (hind-limb) p <0.001. In hypertrophic muscle (hemidiaphragm) there was a significant increase in both total rpS6 protein expression p < 0.001 and phosphorylated rpS6 protein expression p < 0.001. The results show a marked up regulation of rpS6 and phosphorylated rpS6 in hypertrophic denervated skeletal muscle and of phosphorylated rpS6 in denervated atrophic skeletal muscle. Further studies are necessary in order to understand the significance of increased rpS6 phosphorylation in denervated atrophic as well as hypertrophic skeletal muscle.