Intermittent hypoxic exposure with exercise training is based on the assumption that brief exposure to hypoxia is suYcient to induce beneWcial muscular adaptations mediated via hypoxia-inducible transcription factors (HIF). We previously demonstrated (Mounier et al. Med Sci Sports Exerc 38:1410–1417, 2006) that leukocytes respond to hypoxia with a marked inter-individual variability in HIF-1 mRNA. This study compared the eVects of 3 weeks of intermittent hypoxic training on hif gene expression in both skeletal muscle and leukocytes. Male endurance athletes (n = 19) were divided into an Intermittent Hypoxic Exposure group (IHE) and a Normoxic Training group (NT) with each group following a similar 3-week exercise training program. After training, the amount of HIF-1 mRNA in muscle decreased only in IHE group (¡24.7%, P < 0.05) whereas it remained unchanged in leukocytes in both groups. The levels of vEGF121 and vEGF165 mRNA in skeletal muscle increased signiWcantly after training only in the NT group (+82.5%, P < 0.05 for vEGF121; +41.2%, P < 0.05 for vEGF165). In leukocytes, only the IHE group showed a signiWcant change in vEGF165 (¡28.2%, P < 0.05). The signiWcant decrease in HIF-1 mRNA in skeletal muscle after hypoxic training suggests that transcriptional and post-transcriptional regulations of the hif-1 gene are diVerent in muscle and leukocytes.