Humeral torsion and its influences on throwing athletes have been an evolving topic of much discussion over the past 20 years. Numerous studies have explored the development of this adaptive response in adolescent throwers and its implications. Other studies have examined performance with regard to humeral torsion in adolescent, collegiate, and professional throwers. Evaluation and diagnosis of humeral torsion have also been described in the literature. Injury patterns associated with humeral torsion have been discussed. The purpose of this chapter is to highlight these topics.