Research into the hypoxic tumour microenvironment is accelerating and the reversal of hypoxia is increasingly being suggested as a mechanism for improving cancer treatment. Recent studies have suggested that hypoxia is also a feature in prostate cancer and is associated with a poor prognosis. Hypoxia has been shown to cause radio-resistance and hence hamper one of the major treatments for prostate cancer. However, unlike other solid tumours, such as cervical and head-and-neck cancer, there are inconsistencies and unanswered questions about the relevance of hypoxia in prostate cancer. This review outlines the role of low-oxygen conditions in prostate cancer and the areas where further studies are required.