Diffusion kurtosis MRI was used to evaluate the longitudinal changes in a tumor microstructure of a rat model of glioblastoma. F98 tumor cells were injected into six rat brains and imaged longitudinally 8, 11 and 14 days post-implantation. For DKI, an EPI-DTI sequence was used with 2 b-values (1000-2000 s/mm2) and 15 directions. Diffusional kurtosis parameters increased in the tumor compared to the contralateral healthy brain. No significant change with time in the tumor was observed for any diffusion or kurtosis parameters.