It is well known that low levels of tissue oxygen (pO2) protect tumour cells from ionising radiation and some chemotherapeutic agents. Thus, numerous studies have been aimed at developing methods to measure tissue oxygenation. An initial discussion of some of the traditional methods for measuring oxygenation is included, followed by a discussion of magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) methods for measuring tumour and normal tissue oxygenation. The latter methods are of interest because of the non-invasive nature of magnetic resonance (MR). Some of the MR methods described herein include: 31P MRS, 1H MRS and MRI, and 19F MRS and MRI. Each method is detailed, including a brief assessment of its ability to measure tumour oxygenation and its potential for clinical application.