The first few sections of this chapter chronicle the development of the modern sports helmet and the evolution of their performance standards in the context of research in the biomechanics of head trauma. How this research has been employed in performance testing protocols and how this may have influenced helmet design is reviewed. The design of the testing protocols, the biofidelity of the test devices, the injury assessment functions available and the failure limits employed in recognized standards are all issues that bear on the application of biomechanical fundamentals. The second half of this chapter discusses practical considerations in helmet design including the specification of performance requirements and material and design constraints. Recent advances in helmet designs and test methods are also briefly reviewed.