Hypoxia‐inducible factor 1 (HIF‐1) is a heterodimeric transcription factor composed of HIF‐1α and HIF‐1β subunits that functions as a master regulator of oxygen homeostasis. Oxygen‐dependent hydroxylation of HIF‐1α provides a mechanism that allows changes in oxygenation to be transduced to the nucleus, leading to changes in gene expression. Hypoxia‐inducible factor 1 plays critical roles in development, physiology and disease pathogenesis. Analyses of mice that are heterozygous for a null allele at the locus encoding the HIF‐1α subunit have demonstrated that partial deficiency of HIF‐1 is sufficient to impair multiple physiological responses to continuous and intermittent hypoxia.