PURPOSE: We attempted to determine the differences in frequency, as well as clinical, radiologic characteristics of atypical femoral fracture between groups of patients who have taken bisphosphonate and those who have not by conduct of a retrospective analysis of patients with low energy subtrochanteric and shaft fractures of the femur. MATERIALS AND METHODS: We conducted a retrospective study of 44 cases of 41 female patients over 60 years old who underwent surgery due to femoral shaft/subtrochanteric fractures from August 2001 to October 2011. The patients were divided into two groups: Group A, 22 cases in 19 patients with a history of bisphosphonate treatment; Group B, 22 cases in 22 patients without a history of bisphosphonate treatment as a control group. We assessed the duration of bisphosphonate treatment, presence of prodromal symptoms, and radiological results, and compared age, BMD results, union period, and nonunion rate between the two groups. RESULTS: Mean medication period was 56.8 months(12-132 months) and prodromal symptoms were observed in one case. Lateral cortical thickening and transverse fracture with a medial cortical bone beak were observed in all patients of Group A, and contralateral cortical hypertrophy of the femur was noted in 15 patients(17 cases) (77.3%). Mean age was 73.2 years in Group A and 78.2 years in Group B, which showed significant difference (P=0.021), while no difference was observed in BMD, union period, and nonunion rate. CONCLUSION: An atypical femoral fracture can occur in the subtrochanteric or shaft of the femur. The typical radiological characteristics of this fracture are lateral cortical thickening and transverse fracture with a medial cortical bone beak and contralateral abnormality of cortical bone. Findings of this study suggest that medical practitioners should be careful of atypical fractures with osteoporosis patients who use prolonged bisphosphonate.