Human HeLa cells were either kept in a hypoxic environment or under normoxic conditions. 137 proteins were found to be regulated, with maximum alteration of 18-fold. In particular, three clusters of differentially regulated proteins were identified, showing significant up-regulation of glycolysis and down-regulation of mitochondrial ribosomal proteins and translocases. This interaction is likely orchestrated by HIF-1. We also investigated the effect of hypoxia on the cell cycle, which is arrested at a restriction point in G1, and shows a prolonged S phase under these conditions.