Sixty-one menisci in 60 patients who underwent preoperative MRI and subsequent arthroscopic operation for symptomatic isolated semilunar lateral meniscus tears were evaluated. The MRI criterion of reparability was the presence of a longitudinal or oblique high signal intensity line within 3 mm meniscosynovial junction without a high signal intensity area in the meniscal body, and the criterion of irreparability was high signal intensity line greater than 5 mm from the meniscosynovial junction and/or abnormal high intensity area in the meniscal body. Perioperatively the menisci were repaired for longitudinal unstable tears located at the outer one-half and were excised for other type of tears. Consequently 30 menisci were repaired, and 31 menisci underwent menisectomy. Overall, MRI was useful for detecting the meniscus tears in 42 (69%). The accuracy and sensitivity of MRI in predicting reparability were 91% and 33%; for predicting irreparability the respective values were 90% and 90%. The findings of this retrospective study suggest that MRI is not always useful in predicting reparability of the symptomatic isolated lateral semilunar meniscus tears, and that the most symptomatic cases with normal MRI are reparable.