Serum neutralizing, nasopharyngeal neutralizing, and IgA antibodies to polioviruses 1, 2, and 3 were detected in preterm and term infants who had received three doses of an enhanced-potency inactivated poliovirus vaccine at 2, 4, and 12 months of age. After the third dose of this vaccine, 95% or more of the infants tested had detectable serum neutralizing antibodies to polioviruses types 1, 2, and 3. Nasopharyngeal neutralizing and IgA antibodies were detected in 43% to 91% of the infants. The peak geometric mean titers of serum and nasopharyngeal antibodies against polioviruses types 1, 2, and 3 were similar for both groups. These preliminary data indicate that preterm infants are capable of mounting systemic and local immune responses to enhanced-potency inactivated poliovirus vaccine that are comparable to those made by term infants.