Fifty-four femoral neck fractures in young adults (20-50 years old; Group I) were compared with 397 fractures in the elderly population (older than 60 years of age; Group III). Patients in Group I were more frequently men and had often sustained vertical shear fractures in high-energy injuries. Treatment consisted mostly of open reduction and internal fixation (88%). There were no infections, pulmonary embolisms, or deaths. The rate of avascular necrosis was 10%; the rate of delayed union or nonunion, 17%; and the revision rate, 20%. Reoperation did not preclude an excellent final outcome. Patients in Group III were mostly women who fell at home and sustained an adduction fracture, which was most frequently (80%) treated with a cemented monopolar arthroplasty. Complications included pulmonary embolisms (3.5%), other cardiovascular complications (8%), and respiratory complications (7%). The death rate during hospitalization was 6.5%; for the first year after surgery it was 21%. These complications were not more frequent with either hemiarthroplasty or internal fixation. Local complications required revision of 17% of the cases treated with internal fixation and 1.4% of the patients treated with hemiarthroplasty. In the entire series, the deep infection rate without prophylactic antibiotics was 1.5%; with prophylactic systemic antibiotics it was 0.7%. The incidence of pulmonary embolism without thromboprophylaxis was 3.2%; with fixed-dose, subcutaneous heparin it was 1.1%. Of those treatments tested, open reduction and internal fixation with cancellous bone screws (for the younger patients) and hemiarthroplasty (for the elderly patients) yield the best short-to-midterm results. In addition, thromboprophylaxis with fixed-dose subcutaneous heparin and systemic antibiotic prophylaxis will continue to be used.