Each annual birth cohort in the United States comprises approximately 4 million infants. Maintaining the gains in vaccination coverage achieved during the 1990s among these children poses a continuing challenge for public health practitioners. The National Immunization Survey (NIS) provides estimates of vaccination coverage among children aged 19-35 months for each of the 50 states and 28 selected urban areas. This report summarizes NIS results for 2003, which indicated substantial increases nationwide in coverage with > or =1 dose of varicella vaccine (VAR) and > or =3 doses of pneumococcal conjugate vaccine (PCV) and the highest coverage ever for all vaccines; however, wide variability in coverage continues among states and urban areas. Continued vigilance is needed to maintain high levels of coverage, and sustained efforts will be required to reduce geographic disparities in coverage.