Prostate cancer is the most common solid cancer occurring among men in the US. Diffusion-weighted MR imaging plays a complementary role to T2-weighted images in identifying regional changes in prostate tissue. Here, we fit the diffusion decay signal from patients using the stretched-exponential and the kurtosis models and compare the results with MR guided prostate biopsy histology. Our results showed that the kurtosis and stretched exponential models fit to multi-b values diffusion data have the potential to distinguish benign from malignant lesions. These model parameters identify tissue heterogeneity and structures that may be useful in the grading of prostate cancer.