This study assessed the effect of an oral stimulation program on the maturation of sucking skills of preterm infants. Thirty-two preterm infants (13 males, 19 females), appropriate size for gestational age (gestational age at birth 28 wks, SD 1.2wks; birthweight 1002g, SD 251g), were randomly placed into experimental and control groups. The experimental group received a daily 15-minute oral stimulation program, consisting of stroking the peri- and intra-oral structures, for 10 days before the start of oral feedings. Sucking measures were monitored with a specially-designed nipple-bottle apparatus. Results indicate that the experimental group achieved full oral feedings 7 days sooner than the control group, and demonstrated greater overall intake (%), rate of milk transfer (mL/min), and amplitude of the expression component of sucking (mmHg). There was no difference in sucking stage maturation, sucking frequency, and amplitude of the suction component of sucking. Endurance, defined as ability to sustain the same sucking stage, sucking burst duration, and suction and expression amplitudes throughout a feeding session, was not significantly different between the two groups. The stimulation program enhanced the expression component of sucking, resulting in better oral feeding performance.