Despite considerable research effort, the incidence of whiplash injury during automotive collisions has continued to rise. This is due, at least in part, to a limited recognition of biomechanical injury mechanisms and factors influencing injury risk. While automotive safety modifications reduced injury risk in some cases, impact on the overall whiplash incidence was limited. This is likely attributable to significant occupant-related differences that have a profound impact on injury risk. Many of those differences were outlined in research studies, and examples include female sex and the associated sex-based anthropometrical variation that can affect seating orientation; cervical spinal posture; and anatomical attributes, including cervical column slenderness and neck muscle morphometry. This review highlights these anatomical attributes and explains, based on biomechanical concepts, the method by which these attributes may alter cervical spine response during automotive rear impacts to affect injury risk. The biomechanical explanations are based on existing studies that have incorporated postmortem human subjects, computational models, and anthropomorphic test devices (ie, crash test dummies), as well as medical imaging in human volunteers. These biomechanical explanations may provide improved understanding of injury risk.