The erythropoietin (Epo) is a model of proteins expressed upon hypoxia, regulated at the transcriptional and post transcriptional levels. The Hypoxia Induced Factor (HIF-I) activates the transcription of genes which exhibit the Hypoxia Regulatory Element (HRE). In addition the mRNA is stabilized upon hypoxia, increasing the hormone synthesis. The Epo gene is a convenient reporter gene to develop gene delivery systems and the in vivo regulation of the transgene. The beta thalassemia and acquired chronic anemias may benefit from the Epo gene transfer and expression, if it becomes safe, tunable and inexpensive.