A proven method to increase vaccination rates in primary care is a standing orders program (SOP) for nonphysician staff to assess and vaccinate eligible individuals without a specific written physician order. This study describes a mixed methods approach to examining physicians' beliefs and attitudes about and adoption of SOPs for adult immunizations, specifically, influenza and pneumococcal polysaccharide vaccine. Focus groups and in-depth interviews of physicians, nurses, practice managers, and the medical director of a managed care health plan were conducted. Results were used to enrich a concise survey based on the Awareness-to-Adherence model of physician behavior and previous research, which was mailed to 1,640 general internists and family physicians nationwide. Barriers to SOPs identified through qualitative methods were lack of interest in changing the status quo, a physician-dominated hierarchy, and fear of malpractice. Facilitators included having an electronic medical record and a practice culture that was open to change. The survey (response rate 67%) confirmed the facilitators and further identified patient, physician, and practice factors that served as barriers to establishing and maintaining SOPs. This mixed methods approach provided the opportunity to develop a tailored and practice-oriented survey for examining the contextual factors influencing clinical providers' decisions to implement SOPs for adult immunization.