A total of 1750 knees were prospectively evaluated using a high-resolution noninvasive axial computed tomography (CT) scanning technique. A total of 203 knees underwent subsequent arthroscopic or arthrographic evaluation. In this group, the sensitivity of CT for the detection of a torn meniscus was 88.5%; the specificity was 95.5%; and the accuracy was 91.5%. An additional 270 knees were prospectively evaluated by both CT and magnetic resonance imaging (MRI) to determine the ability of both techniques to characterize knee menisci in patients believed to have meniscal tears. Of these knees, 94 were subsequently examined by arthroscopy. In this group, the overall accuracy of MRI for detecting a torn meniscus was 89.5% and for CT it was 92.2%. Properly performed, both CT and MRI are accurate and effective methods for noninvasively evaluating meniscal abnormalities in the acutely injured knee. The protocol for CT and MRI meniscus imaging as well as interpretation are presented in addition to their relative roles with respect to arthrography and arthroscopy.