Diphtheria, tetanus, and pertussis (DTP) immunization data were collected on 103 special care nursery graduates in our neonatal follow-up clinic to determine whether DTP immunization schedules were significantly delayed relative to recommendations of the American Academy of Pediatrics (2, 4, and 6 months for DTP 1, 2, and 3, respectively). An inverse correlation was found between birth weight and immunization for first, second, and third DTP (r = 0.319, P less than .01; r = .205, P less than .05; and r = .236, P less than .05, respectively). We subsequently conducted a mail survey to determine the DTP immunization policy present in effect in 25 neonatal intensive care units in the United States and Canada. The survey indicates that procedural approaches remain markedly heterogeneous, and 10 of 25 (40%) units have no existing policy for implementation of DTP immunization. These data suggest that special care nursery populations are at potential risk for pertussis, which requires a conscious implementation of DTP immunization by the special care nursery, the follow-up clinic personnel, and the primary care physician.