Temperature measurement using magnetic resonance imaging (MRI) of water self-diffusion is investigated. Diffusion images and derived temperatures are obtained in polyacrylamide gel phantom. The temperatures measured from MRI are compared with those from temperature probes to verify their accuracy. In general, the difference between temperatures determined from MRI diffusion images over 0.3 cm3 regions of interest and from temperature probes were 0.2 degrees C. It is concluded that current MRI technology allows noninvasive temperature tomography that is comparable with invasive thermometry with respect to temperature accuracy, has spatial and time resolutions that would be useful in hyperthermic oncology.