The present invention provides methods of determining the microvascular density of tumors. The methods generally comprise creating a digital image of a defined cross section of the tumor, determining the cross-sectional surface area of vascular tissue in the section of the tumor, determining the total cross sectional area of the section of the tumor, calculating the ratio of the cross sectional surface area of the tumor to the total cross sectional area of the section of the tumor, and thereby determining the microvascular density of the tumor. The digital image of the tumor may preferably be created using image processing software and the image may be displayed on a computer screen. The image may be digitally dissected by removing from the image all non-vascular tissue. This approach produces reproducible results that match the results generated by functional MRI assessments of blood perfusion of the tumors.