Insufficient supply of oxygen, i.e. hypoxia, typically occurs in a broad range of solid tumours due to aberrant vasculature. It is a key component of tumour microenvironment that affects many biological processes at molecular, cellular and tissue levels. Adaptive responses to oxygen deficiency shape signal transduction, cell metabolism, proliferation, differentiation, survival, angiogenesis, immunosurveillance etc. and thereby contribute to tumour invasion and metastasis. Presence of tumour hypoxia is significantly associated with poor prognosis and therapy resistance. Therefore, it represents a clinically relevant phenomenon that can be exploited for improvement of existing diagnostic and treatment procedures as well as for development of new targeted strategies. This book summarizes the current state of knowledge on hypoxia-regulated pathways and their biological consequences and describes promising approaches to clinical application of this knowledge. It is the first concise and complex guide to understanding principal basic and medical aspects of tumour hypoxia.