BACKGROUND Barriers to adult immunizations persist as current rates for pneumococcal polysaccharide vaccine (PPV) receipt among eligible adults remain below national goals. This study investigated potential barriers to patients receiving the PPV, including predisposing, enabling, environmental and reinforcing factors among physicians from a variety of practice and geographic settings. METHODS Participants were 60 primary care physicians from inner-city, rural, suburban, and Veterans Affairs practices, which included adults aged 65 years and older. Elderly patients able to complete a telephone interview were randomly selected from each physician's practice. RESULTS Self-reported PPV vaccination status was significantly related to physician report of routinely providing PPV to their patients and to the practice providing immunization clinics or other immunization promotion programs. Physicians who were highly unlikely to refer uninsured adults to health departments for immunizations had a significantly higher percentage of patients reporting receipt of PPV (P = .03). CONCLUSIONS Enabling and environmental factors related to physicians, such as economic and insurance issues, were significant barriers to PPV vaccination. Vaccination rates might be improved through efforts that reduce likelihood of referral for immunizations and office systems that support immunization, such as patient and provider reminders and express vaccination clinics.