Objective: Management of vertical femoral neck fractures in young adults has been a challenging clinical problem, resulting in mixed clinical outcomes. A thorough understanding of the fracture morphology for this injury pattern is lacking, which may contribute to frequent failures of treatment. This study is designed to produce a detailed description of the pathoanatomy of these fractures, which may ultimately be helpful in developing more informed reduction and fixation strategies. Design: Retrospective study of patient records, plain radiographs, and computed tomography scans to determine the morphology the Pauwels III femoral neck fractures (coronal angle >50 degrees) in young adults. Setting: Two level I and 1 level II regional trauma centers. Patients: All patients 18-49 years of age with a surgically repaired, high-energy high shear angle (>50 degrees) femoral neck fracture from January 1, 2007, to December 31, 2010. Methods: One hundred thirty-six adult patients younger than 50 years were identified with a femoral neck fracture in the study period, of whom 33 met all study criteria. We evaluated plain radiography and computed tomography data including fracture orientation, comminution, deformity, characteristics of the inferomedial fracture spike, and the associated inferomedial calcar's cortical buttress. Results: The vertical (coronal) fracture averaged 60 degrees and axial fracture obliquity averaged 24 degrees with relative deficiency of the posterior neck on the head-neck fragment. Major femoral neck comminution (>1.5 cm in any dimension) was identified in 96% of cases, mostly located in the inferior (94%) and posterior (82%) quadrants. The apical fracture spike of the head segment was found to be in line (within 10 degrees) of the neck-shaft axis on the proximal femur 63% of the time. Deformity in external rotation averaged 44 degrees (range, 10-68 degrees) and shortening of the femur averaged 1.8 cm (range, 0.9-4.4 cm). Conclusions: This study investigated the fracture morphology of isolated, high shear angle femoral neck fractures in young adults, which may ultimately lead to improved operative reduction and fixation tactics. Given this injury's characteristic findings, including fracture orientation, deformity, and comminution, surgeons should be cognizant of this pattern's innate instability and potential for treatment failure with typical implant constructs.