This study was conducted to compare the difference between left and right extension and flexion isokinetic muscular strength of the knee, shoulder, and trunk to compare absolute and relative strength in lightand heavy weight Ssireum athletes. Fourteen professional Ssireum athletes were divided into the light (Taebaek and Geumgang) and heavy (Halla and Baekdu) groups according to the body weight. Anthropometric measurements and isokinetic strength (knee: 60º/sec, shoulder: 30º/sec, and trunk: 30º/sec) were assessed for the absolute and relative peak torque values. Left (227.6±48.7 vs 247.0± 23.1 Nm, p=0.05) and right knee (233.7±32.0 vs 266.1±20.5, p=0.05) extension strength in absolute values were significantly different between the groups. Trunk’s extension (318.7±37.9 vs 351.2±57.4 Nm, p=0.03) and flexion (249.8±33.0 vs 302.1±42.4 Nm, p=0.03) strength also showed significant difference between the groups. Significant differences were observed for all relative values except for the left knee and trunk flexion. As for the flexion and extension strength ratios, the shoulder extension to flexion ratios of the light group was 1.32 (p=0.02) times and the heavy group was 1.01-0.98 (p=0.34). The trunk extension strength was 3.6 times that of the body weight in the light group and 2.8 times that of the body weight in the heavy group. Heavy Ssireum athletes’ absolute flexor peak torques were higher in the knee and trunk than in the light athletes. Also, the weight per weight of light athletes had relatively higher strength than the heavy athletes. In addition, the muscle strength ratio was higher in the light athletes. This study suggests that isokinetic strength is different in heavy and light weight class Ssireum athletes.