The prevention of life-threatening childhood infections through vaccination is a remarkable achievement in the history of medicine. Although 98% of all American children are fully immunized at age 5 to 6 years because state laws require it for school entry, in 1991 less than half of children younger than 2 years of age were up to date for their diphtheria, tetanus, and pertussis (DTP); polio; measles, mumps, and rubella (MMR), and Haemophilus influenzae type b (HIB) immunizations. These children are at greatest risk for lifethreatening infection. The last decade has seen many changes in the recommendations for routine childhood immunization. The resurgence of measles led to the addition of a second measles immunization. The introduction of the HIB vaccine has had a significant impact on the incidence of dreaded childhood meningitis. The effort to reduce adverse events associated with the pertussis component of the DTP vaccine resulted in the development of a new pertussis vaccine. The oral polio vaccine (OPV) is still being used with much debate on the merits of the inactivated polio vaccine (IPV). The hepatitis B vaccine was recently incorporated into the childhood immunization schedule in an A crucial link m the chain of optimal preventive health care will continue to involve those who prescribe, order and administer vaccines.]