The purpose of this review is to provide an overview of the methods available for imaging tissue oxygenation. The following imaging methods are reviewed: phosphorescence, near-infrared (NIR), positron emission tomography (PET), magnetic resonance imaging ((19)F MRI and BOLD MRI), and electron paramagnetic resonance (EPR). The methods are based on different principles and differ in their ability to accurately quantify tissue oxygenation, either the absolute value of a particular measure of oxygenation (partial pressure of oxygen, concentration), or a parameter related to it (oxygen saturation). Methods that can provide images of relative changes in oxygenation or visualization of hypoxia in a specific tissue of interest are also considered valuable tools for biomedical research and clinical applications.