Objective: Immunization rates are static in the United States. Risk factors for not being up to date (UTD) include ethnicity and lower socioeconomic status. Reminder cards increase immunization rates in urban settings. Their effect in poor, Latino, and rural children is unknown. Background: Language-appropriate reminder cards were sent to active patients not UTD listing the vaccines missing; the card served as the physician order for the vaccine. Missed opportunities were addressed through discussion with staff and posters in patient care rooms. UTD rates before and after intervention were measured. Results: Dual-purpose reminder/order cards increased the rate of UTD from 61.3% to 73.4%; children living near the clinic, patients who speak only Spanish, and Latinos overall showed preferential effectiveness. Children eligible to participate in the Vaccines for Children program had similar increases in UTD rates but had lower baseline and final UTD rates than did children not eligible for the Vaccines for Children program. The rate of missed opportunities did not change. The number of children to whom reminder cards needed to be sent for them to become fully immunized is 8 (number needed to treat). Conclusions: In poor, rural, and Latino populations, language-appropriate reminder/order cards increase immunization rates.