High rates of preventable diseases such as pneumococcal disease occur among the Navajo despite their universal health insurance through the Indian Health Service. The objective of this study was to determine the proportion of Navajo adults vaccinated with pneumococcal polysaccharide vaccine and to examine key features of vaccination programs of the Navajo Indian Health Service. For this cross-sectional study, medical charts of Navajo patients with vaccine indications were randomly selected and reviewed to determine who had been vaccinated as of January 1, 1999. Among 480 Navajo>or=65 years old, 73% were vaccinated (95% confidence interval [CI]: 69%-77%). Among 111 Navajo 18-64 years old with vaccine indications, 54% were vaccinated (95% CI: 45% -63%). Vaccination programs utilized extensive public health nursing, home visits, standing orders, and "express lane" clinics. In spite of excellent delivery systems and universal healthcare, the proportion of Navajo persons vaccinated was still below the goals for Healthy People 2010 of having 90% of persons>or=65 years old vaccinated and 60% of high-risk persons 18-64 years old vaccinated.