PURPOSE: To determine the time of magnetic resonance(MR) signal intensity changes in denervated skeletal muscle and to compare MR imaging with electromyography(EMG) in the evaluation of peripheral nerve injury. MATERIALS AND METHODS: We evaluated MR imagings of denervated muscles after experimental transection of the sciatic nerve in five rabbits using 1.0T MR unit. MR imaging and EMG were performed 3 days and 1, 2 and 3 weeks after denervation. T1-weighted images(T1-WI), T2-WI and Short Tau Inversion Recovery(STIR) images were obtained. The signal intensity (SI) of muscles in the denervated and normal sides were visually and quantitatively compared. After measuring the SI of the normal and abnormal areas, the time of SI change was determined when there was significant difference (P<0.05) of SI between the normal and denervated sides. RESULTS: On STIR images, two of the five rabbits showed significant SI changes at the third day(P<0.05) and all showed significant changes(P<0.05)at the first week. On T2-WI, one rabbit showed significant SI changes at the third day, and all showed significant SI changes at the first week. On T1-WI, significant SI changes were seen in one rabbit at the second week and in one at the third. One week after denervation, all showed denervation potential on EMG. CONCLUSION: This study suggests that MR imaging using STIR images is a useful method in the evaluation of denervated muscle, and that MR signal changes of denervated muscle may precede EMG changes after denervation. To localize and to determine the severity of the peripheral nerve injury, future analysis of the distribution of abnormal MR SI in denervated muscles would be helpful.