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Magnetic resonance microimaging was used to measure dif-fusion decay over an extended b-factor range in a formalin-fixed normal prostate sample and a Gleason pattern 314 can-cer tissue sample. The coefficients of biexponential fits to dif-fusion decay data from 1600 voxels of dimension 160 3 160 3 160 mm3 in each sample were correlated with underlying epithelial and stromal compartment partial volumes estimated from high-resolution apparent diffusion coefficient (ADC) data (40 3 40 3 40 mm3 voxels) from the same tissue. In the nor-mal tissue sample, the signal fractions of the low and high ADC components of the biexponential fits correlated linearly with partial volumes of epithelial tissue (R2 5 0.6) and stromal tissue (R2 5 0.5), respectively. Similar but weaker correlations were observed in the cancer sample. Epithelium-containing high spatial resolution voxels appeared to be composed o