Purpose The purpose of this study was to evaluate the clinical results and prognostic factors of arthroscopic surgeries for tears of the discoid lateral menisci. Materials and Methods From March 1997 to September 2005, 260 patients received arthroscopic surgeries due to discoid lateral menisci tears. Among these patients, 179 knees in 168 patients were followed up for at least 2 years and were enrolled into this study. The following prognostic factors were evaluated: sex, age, symptom duration, and type of meniscal tear. Visual analogue score (VAS), Lysholm score, and Ikeuchi grade were assessed as clinical results of arthroscopic surgeries. Results The mean VAS and Lysholm score improved at the last follow-up. According to the Ikeuchi grade, 104 cases were rated as excellent, 51 cases as good, and 23 cases as fair. Male sex (p<0.033), age younger than 20 years (p=0.0474), and symptom duration less than 12 months (p<0.044) were good prognostic factors. However, there was no correlation between tear types of discoid lateral menisci and clinical results. Conclusions Sex, age, and symptom duration could be significant prognostic factors of arthroscopic surgeries for tears of discoid lateral menisci.