CONTEXT: Approximately 62% of all cheerleaders sustain some type of orthopaedic injury during their cheerleading careers. Furthermore, the occurrence of such injuries has led to inquiry regarding optimal prevention techniques. One possible cause of these injuries may be related to inadequate conditioning in cheerleaders. OBJECTIVE: To determine whether a strength and conditioning program produces quantifiable improvements in anterior glenohumeral (GH) laxity and stiffness. DESIGN: Descriptive laboratory study. SETTING: University laboratory. PATIENTS OR OTHER PARTICIPANTS: A sample of 41 collegiate cheerleaders (24 experimental and 17 control participants) volunteered. No participants had a recent history (in the past 6 months) of upper extremity injury or any history of upper extremity surgery. INTERVENTION(S): The experimental group completed a 6-week strength and conditioning program between the pretest and posttest measurements; the control group did not perform any strength training between tests. MAIN OUTCOME MEASURE(S): We measured anterior GH laxity and stiffness with an instrumented arthrometer. We conducted a group × time analysis of variance with repeated measures on time (P < .05) to determine differences between groups. RESULTS: A significant interaction was demonstrated, with the control group having more anterior GH laxity at the posttest session than the strengthening group (P = .03, partial η2 = 0.11). However, no main effect for time (P = .92) or group (P = .97) was observed. In another significant interaction, the control group had less anterior GH stiffness at the posttest session than the strengthening group (P = .03, partial η2 = 0.12). Main effects for time (P = .02) and group (P = .004) were also significant. CONCLUSIONS: Cheerleaders who participate in a shoulder-strengthening program developed less anterior GH laxity and more stiffness than cheerleaders in the control group.