STUDY DESIGN Single-group repeated-measures design. OBJECTIVES To investigate the ability of the wall slide exercise to activate the serratus anterior muscle (SA) at and above 90 degrees of humeral elevation. BACKGROUND Strengthening of the SA is a critical component of rehabilitation for patients with shoulder impingement syndromes. Traditional SA exercises have included scapular protraction exercises such as the push-up plus. These exercises promote activation of the SA near 90 degrees of humeral elevation, but not in positions above 90 degrees where patients typically experience pain. METHODS AND MEASURES Twenty healthy subjects were studied performing 3 exercises: (1) wall slide, (2) plus phase of a wall push-up plus, and (3) scapular plane shoulder elevation. Three-dimensional position of the thorax, scapula, and humerus and muscle activity from the SA, upper and lower trapezius, and latissimus dorsi were recorded. The magnitudes of activation for each muscle at 90 degrees, 120 degrees, and 140 degrees of humeral elevation were quantified from EMG records. Repeated-measures analyses of variance were used to determine the degree to which the different exercises activated the SA at the 3 humeral positions. RESULTS The intensity of SA activity was not significantly different between the 3 exercises at 90 degrees of humeral elevation (P = .40). For the wall slide and scapular plane shoulder elevation exercises, SA activity increased with increasing humeral elevation angle (P = .001), with no significant differences between the 2 exercises (P = .36). CONCLUSION The wall slide is an effective exercise to activate the SA muscle at and above 90 degrees of shoulder elevation. During this exercise, SA activation is not significantly different from SA activation during the push-up plus and scapular plane shoulder elevation, 2 exercises previously validated in the literature.