Purpose: The purpose of this study was to compare modified sling exercise and general isometric exercise in patients with shoulder impingement syndrome. Methods: Twenty subjects were studied. The control group, n1 = 10, received instructions for doing general isometric (ISO) exercise. An experimental group, n2 = 10, received instructions for doing push-ups from standing and sitting positions and modified scapular exercises using a sling (3 sets, 3 times per week for 6 weeks). To evaluate the effects of exercise, subjects were evaluated using a visual analog scale for pain, a goniometer for range of motion, and electromyography for onset time of muscle contraction. Statistical analysis was done using the Wilcoxon Signed rank and Mann-Whitney U tests. Results: Pain in the sling group was significantly decreased after 6 weeks of treatment (p<0.05) pain in the general ISO exercise group was not significantly decreased (p>0.05). Flexion and external rotation were significantly increased after 6 weeks of treatment in both groups (p<0.05) and the change in the Sling group was greater than in the ISO group (p<0.05) in the flexion test. Time of onset of contractions in the Sling group for the upper trapezius, lower trapezius and serratus muscle were significantly decreased after 6 weeks of treatment (p<0.05), but the onset time for the middle trapezius did not significantly decrease (p>0.05). Conclusion: Scapular stabilizing exercise using a sling increases range of motion and decreases pain, and onset time of muscle contraction in patients with impingement syndrome.