Although magnetic resonance (MR) imaging is performed routinely, current techniques offer little for evaluation of the peripheral nervous system. An animal model was developed to evaluate the appearance and geographic changes associated with an acute nerve compression injury by MR neurography. Several measurements of signal intensity were made for the contralateral noninjured nerve and each sciatic nerve proximal to the site of compression (PN), at the site of compression (CN), and distal to the site of compression (DN) injury. Mean (+/-SEM) values of the MR nerve/muscle signal intensity ratio were 2.24 +/- 0.08 for normal nerve, 2.29 +/- 0.12 for PN, 3.11 +/- 0.31 for CN, and 4.33 +/- 0.47 for DN. There was a statistically significant geographic variation of nerve/muscle signal intensity ratios along the course of the nerve relative to the site of injury that MR neurography could detect. Magnetic resonance neurography may have significant potential to provide more information about problems such as brachial plexus injuries and peripheral nerve compression.