To assess the impact on clinic-specific vaccination coverage of implementing the Standards for Pediatric Immunization Practices.A nonrandomized intervention trial conducted for 1 year.Two public health clinics in Albuquerque, NM: 1 intervention site and 1 control site, each serving 1 of 4 city quadrants.All children enrolled in the 2 city public health clinics.Implementation of the Standards for Pediatric Immunization Practices.Assessment of up-to-date vaccination coverage levels prior to and at the conclusion of the project. The impact on the proportion of children who dropped out of vaccination services after receiving 1 dose by 3 months of age.At the intervention site, up-to-date coverage at 12 months of age rose from 57.5% to 80.4%, while levels at the control site decreased from 42.1% to 41.9%. Before the intervention, 24% of children at the intervention site who received the first dose of diphtheria and tetanus toxoids and pertussis vaccine (DTP 1) by 3 months of age failed to receive the third dose of DTP (DTP 3) by 12 months of age vs 5% after the intervention. At the control site, the proportion of children who received DTP 1 by 3 months of age, but not DTP 3 by 12 months of age, increased from 39% to 51%.Implementation of the Standards for Pediatric Immunization Practices in a public health clinic was associated with important increases in vaccination coverage levels and a reduction in the proportion of children who dropped out of vaccination services.