['To determine the relationship between the amount of humeral torsion and a measure of active proprioception in adolescent male throwing athletes.', 'Cross-sectional laboratory study with uninjured subjects.', 'University of Sydney and NSW Institute of Sport.', 'Participants were 16 adolescent male baseball players (15.0-18.1 years old, SD=16.3) holding baseball scholarships at the NSW Institute of Sport.', 'The main outcome measures, active proprioception (shoulder rotation, in 90 degrees of arm abduction moving towards external rotation, using the Active Movement Extent Discriminating Apparatus) and humeral torsion (using an ultrasound-assisted method), were measured bilaterally.', 'A strong (r=0.88) and significant (p=0.001) correlation was found between increasing humeral retrotorsion and better active proprioceptive acuity in the non-dominant arm, while the relation was weaker (r=0.41) and did not reach statistical significance (p=0.120) for the dominant arm.'] Is shoulder proprioception associated with humeral torsion in adolescent baseball players?