BACKGROUND: Adherence with medications to prevent fractures is suboptimal. Patients' perceived need for medication is an important predictor of medication-use behavior. OBJECTIVE: Estimate the associations of patients' perceived need of medication for fracture prevention with objective indicators of fracture risk, patients' concerns about medications, and the quality of the patient-physician relationship. RESEARCH DESIGN: Cross-sectional medical record review and mailed survey. A multivariate path model was used to estimate the associations of predictor variables with perceived need for fracture prevention medication. SUBJECTS: A total of 1155 individuals were prescribed an oral bisphosphonate medication between January 1, 2006 and March 31, 2007 at a large urban multispecialty clinic in the United States. RESULTS: Trust in the prescribing physician, prevalent vertebral fracture on spine imaging, patients' self-reported susceptibility to and perceived severity of fractures, and medication concerns were independently associated with perceived need for medication. Bone mineral density and fracture history were only weakly associated with perceived need for medication. Trust in the physician was associated with perceived severity of fractures but not with self-reported susceptibility to fractures. Patients' perceptions that their physician communicates openly with them and their satisfaction with their physician's decision-making style are strongly associated with their trust in that physician. CONCLUSIONS: Documenting prevalent vertebral fracture may influence patients' perceived need for fracture prevention medication. Patients' trust in their physicians influences perceived need for fracture prevention medication. Patients' perceptions of open physician communication and their satisfaction with their physician's decision-making style are indirectly associated with perceived need for fracture prevention medication.